DE69421434T2 - PCB for optical elements - Google Patents

Description

The present invention relates to a circuit board for mounting an optical device to be used for converting light into electricity or electricity into light, and more particularly, it relates to an optical element circuit board for use in an optical reading device, optical image forming device, optical printer, or the like.

For some time, electronic circuits have been used in a wide range of fields, from office machines to household items or toys, and consequently the development of small-sized, lightweight, high-speed and precise equipment continues. In the field of various forms of image input including high-speed facsimile, scanner, (white-board) copying device or, for example, a copying device based on electrophotography, there is an increasing demand for equipment with high quality, high resolution, manageability of a raster image, while having a simple compact structure and also being able to be manufactured at a low cost.

In the above-mentioned image input devices, optical information is converted into an electrical signal with an image sensor. Fig. 1 is a typical cross section showing an example of a structure of a conventional image sensor. In Fig. 1, a darkening layer 52 is provided on a glass substrate 51 having a narrow cut-out portion to form a slit 52a. The slit 52a extends in the direction perpendicular to the surface of the paper constituting the figure, and Fig. 1 is a cross section taken along the plane perpendicular to the longitudinal direction of the slit 52a. A transparent insulating layer 53 is provided in a manner such that the obscuring layer 52 and slit 52a are covered, and a plurality of light receiving devices 56 and electrodes 54, respectively, are provided on the transparent insulating layer 53 in electrical connection therewith. The light receiving devices 56 are arranged along the longitudinal direction of slit 52a. A transparent protective layer 55 is provided such that the entire area of the transparent insulating layer 53, electrode 54 and light receiving device 56 are covered, and on the surface of the transparent protective layer 55, that is, on the outermost surface of the image sensor, a transparent conductive layer 57 is formed. The image sensor is manufactured as a unit.

In order to read a letter or a number on a manuscript 59 using this image sensor, it is sufficient that the manuscript 59 is placed on the surface of a transparent conductive layer 57 so that the manuscript can be moved in the direction of an arrow shown in the figure with a dotted line with a roller 60, and further, a light source 58 is provided on the side of the glass substrate 51 so that light 61 from the light source 58 passes through the slit 52a and is reflected on the surface of the manuscript 59 to enter the light receiving device 56. By bringing the manuscript into this state with the roller 60, an image is input by line scanning.

Since it has become necessary to provide a plurality of light receiving devices 56 along the longitudinal direction of slit 52a, a light detecting device using an amorphous semiconductor has been used as the light receiving device 56. However, the amorphous semiconductor device has defects such as low light detecting sensitivity, the characteristics tend to deteriorate when exposed to light for a long period of time, and it has a low response rate. Therefore, it is difficult to operate at a fast reading speed when the amorphous semiconductor is used as a light receiving device.

On the other hand, a light receiving device using a crystalline semiconductor is characterized by excellent photosensitivity and high response rate. Therefore, a scanning device composed of a crystal semiconductor-based light receiving device allows high-speed reading. When the image sensor is manufactured using a crystal semiconductor device, it is difficult to manufacture it as a unit, and thus a crystal semiconductor device (LSI chip) and a circuit board are manufactured separately and then a plurality of the light receiving LSI chips are combined with the circuit board in a multi-chip process. In this way, a sensor that is highly sensitive and has a high reading speed is manufactured. In this case, each LSI chip can be checked whether it is suitable or not before it is assembled into a sensor device. Therefore, by selecting only usable light receiving LSI chips, a circuit board for optical LSI chips can be checked before assembly and it becomes possible to increase the yield of sensors, thereby achieving a cost reduction thereof.

The inventor and others have made studies to further improve the image sensor. The inventor and others first studied the structure allowing a minimum clearance between LSI chips and a manuscript in order to realize a low-output light source to be used for reading the manuscript. In particular, the inventor and others studied using an extremely thin glass substrate having a thickness of 0.1 mm or less as a transparent circuit board for mounting the LSI chips, or using a plastic film as a Substrate. The LSI chip described here is of the pure chip type or has a substrate made of gold or aluminum applied thereto as an external connection terminal.

A circuit board having a plastic film or sheet as its base will now be described. Plastic is flexible and an electrode can be easily formed at high productivity on the plastic-made circuit board by sputtering or vacuum deposition while the board is kept at a low temperature. At present, circuit boards having a plastic film or sheet as its base are widely used in parts of equipment which are subjected to large bending or whose weight is to be reduced, but the use of such circuit boards in a wider field is expected to increase along with the progress of higher integration and further reduction in size and weight of electronic equipment.

However, the inventor and others have found that since a circuit board made of plastic is made of an insulating material and is prone to charging, static electricity generated by friction may accumulate on the surface, thereby affecting the semiconductor device mounted on the circuit board. Practically, an error or disturbance is generated in the output signal, which eventually causes a noise or induces an erroneous movement in the circuit connected to this circuit board. When used in a contact type image sensor, and when a manuscript and this circuit board rub against each other, the charging produces a serious influence. There is a stray or parasitic capacitance when the insulating layer is between two conductive layers. When optical semiconductor LSI chips are in the insulating layer, the capacitance causes the noise or crosstalk for the semiconductor LSI chips. The stray capacitance becomes large in the case of a longitudinally directed image sensor.

In the optical reading device, the light from a light source is irradiated onto a manuscript which is moved under a film-like transparent circuit board to read the manuscript, while the light from the light source is reflected in multiple paths between the manuscript and the circuit board. The inventor and others have also found that the light receiving device for reading receives the light reflected in multiple paths, thereby causing an error in the output of the light receiving device, so that reading is sometimes not carried out correctly.

A similar argument to the above also applies to an optical imaging LSI chip having a plurality of light-emitting devices arranged to form an image on a photosensitive object using light from these light-emitting devices.

With respect to a multi-chip type optical device circuit board having a plurality of reading LSI chips (light receiving LSI chips) or image forming LSI chips (light emitting LSI chips) mounted thereon, it is necessary to provide a plurality of electrodes on the optical circuit board for use in 1:1 connection with these devices. In addition, it is necessary to provide an input and an output circuit on the outside of the circuit board for electrically activating these devices and receiving the signals therefrom. Therefore, in this case, experience is required for electrically connecting the input/output circuit and the circuit board to the optical devices, and furthermore, reliability of the connections may decrease. When the reading area is increased by using an image sensor, additional light receiving devices corresponding to the increased reading area are required on the circuit board. which leads to a significant increase in the number of electrodes on the plate.

Therefore, in order to connect the light-receiving LSI chips and the light-emitting LSI chips in a manner of matrix wiring or the like, an aggregated circuit board is provided between the circuit board having the optical device and the input/output circuit. In this case, the connection may be made such that the electrical connection between the circuit board having the optical device and the aggregated circuit board is first carried out and then the aggregated electrodes on the aggregated circuit board and the input/output circuit are connected. By providing the aggregated circuit board, the input/output circuit can access the aggregated electrodes in number less than the number of optical devices, and thus it becomes possible to activate an optional device or to receive a signal from an optional device. However, the aggregated circuit board requires additional cost for manufacturing it, and labor is also required for electrical connection between the circuit board with the optical device and the aggregated circuit board. When electro-optical devices are increased in number, the number of aggregated electrodes will practically increase approximately in proportion to the number of electro-optical devices increased. Therefore, a method that can provide this aggregated circuit board or aggregated electrode at low cost and high reliability is required. It is also desired to provide a circuit board with an optical device together with a function of the aggregated circuit board.

GB-A-2 228 366 discloses a photoelectric converter having light receiving devices in the form of a photosensor array formed by a thin film process on a transparent sensor substrate. This is adhered to a transparent packaging substrate having a wire pattern on its surface. A light-shielding layer defining a window may be provided between the substrates.

According to claim 1 of the present invention, there is provided an optical circuit board for mounting a plurality of LSI chips for emitting and/or receiving light, comprising

a transparent substrate, the transparent substrate including a slit-shaped window portion for transmitting light entering the substrate and/or exiting from a said LSI chip through the substrate;

a plurality of chip connection electrodes provided on a first main surface of the transparent substrate to which the LSI chips are attached in use, the chip connection electrodes being arranged in a row on at least one side of the window part along the longitudinal direction thereof, the chip connection electrodes being elongated and extending from the window part;

a plurality of input/output circuit connection electrodes (I/OCC electrodes) provided on a second major surface of the substrate, the I/OCC electrodes being elongated and extending parallel to each other in the longitudinal direction of the window part, the second major surface being opposite the first major surface with respect to the transparent substrate, and the I/OCC electrodes being mounted on a region of the first substrate corresponding to the region carrying the chip connection electrodes, so that, when viewed in plan view, the chip connection and I/OCC electrodes define a grid pattern with intersections;

electrical connectors penetrating through the transparent substrate in the areas of the intersections, whereby each of the I/OCC electrodes is electrically connected to a respective one or a plurality of chip interconnect electrodes electrodes through one or a plurality of the electrical connectors; and

a plurality of external connection leads electrically connected to the respective ones of the plurality of I/OCC electrodes and provided on the first main surface and/or the second main surface.

A preferred embodiment of the invention can thus be:

an optical circuit board with an aggregated electrode function, thereby reducing the number of connections to external circuits. It preferably also offers one or more of the following features:

high reliability, with the thermal influence at the time of connection to an external circuit reduced to a minimum; avoidance of electrostatic charge, even when a manuscript and the circuit board rub against each other; no stray and parasitic capacitance; protection against multi-path reflection of light from a light source between the light source and the manuscript and the ability to mount a semiconductor device close to the surface of the optical circuit board.

Preferred embodiments may be:

an optical circuit board in which unnecessary light entering a slit is reduced, the slit in the optical circuit board being provided for passing the light from a light source therethrough;

an optical circuit board in which an electrode and a semiconductor device are mounted in conjunction with increased reliability;

an optical circuit board on which LSI chips can be easily mounted.

An optical circuit board according to the present invention will be described below. The optical circuit board of the present invention is applicable to various uses bar, but representative of assembling an image sensor of an optical reading device by mounting one or more light-receiving LSI chips or a recording head for an optical imaging device such as an optical printer by mounting one or more light-emitting LSI chips.

In the present invention, LSI chip means an electronic device having one or more light-detecting cells or one or more light-emitting cells. Preferably, the LSI chip is an integrated circuit of these light-receiving and/or emitting cells attached to a semiconductor substrate. For example, a photodiode die (die = silicon wafer), a photodiode array, a CCD (charge-coupled device) image pickup device, an LED die, an LED array, an LD (laser diode) die, an LD array or the like are used as LSI chips of the present invention.

When the image sensor is assembled by using the optical circuit board of the present invention, the light receiving LSI chip is bonded to an electrode on a first main surface. In this case, it is preferable to use the light receiving LSI chip having leads for connection provided thereon. The light receiving LSI chip is arranged on the first main surface side with its light receiving surface facing the window part. As for the image sensor, since it is common to construct the image sensor for detecting light emitted from a light source and reflected onto a manuscript, the image sensor is assembled such that the manuscript is arranged on the second main surface, light from the light source enters the transparent substrate from the first main surface side to penetrate the window part, then the light is reflected from the manuscript and again penetrates the window part to enter the light receiving LSI chip. At this time, it is necessary to adjust the light temperature It is necessary to arrange the light-receiving LSI chips carefully so that the light from the light source can enter the window part without being affected by the light-receiving LSI chips. More specifically, it is necessary to arrange the light-receiving LSI chips so that the entire space to the right above the window part is not covered. Since the manuscript and the image sensor are usually moved relative to each other for reading the image data on the manuscript, it is preferable to arrange the image sensor with the longitudinal direction of its window part facing and transverse to the direction of this relative movement.

In assembling an image forming device such as the optical printer by using the optical circuit board of the present invention, the light emitting LSI chips are attached to the electrodes on the first main surface so that the light emitting surfaces of the LSI chips are aligned with the window part. In this case, it is preferable to use the light emitting LSI chips having lead wires thereon. The light emitted from the light emitting LSI chips in response to the recording signal penetrates the window part to enter the surface of the photosensitive material arranged on the second main surface side. Although the photosensitive material is moved relative to the light emitting LSI chips for recording, it is usually preferable to arrange the longitudinal direction of the window part so as to cross the direction of the relative movements of the photosensitive material. If the photosensitive material has a cylindrical shape, the rotation axis thereof should be parallel to the longitudinal direction of the window part.

A transparent substrate to be used for the optical circuit board of the present invention should preferably have high transparency with respect to various lights passing through the window portion. The value of transparency is at least not less than 70%, and preferably not less than 80%. As a base material for composing the transparent substrate, it is desirable to use a synthetic resin. plastic film from the viewpoint of the following properties of the plastic film, such as convenient handling and processability, flexibility, possibility of continuous production, and thin film thickness allowing a small transmission distance between manuscript and light sources, light-reading LSI chips or light-emitting LSI chips. As preferred base materials, for example, plastic films made of polyester such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), or plastic films made of homopolymer or copolymer such as polyamide, polyether, polysulfone, polyethersulfone (PES), polycarbonate, polyarylate, polyetherimide, polyetheretherketone (PEEK), polyimide, polyparabanic acid are used. In addition, the film thickness is usually in the range of 5 to 500 µm, suitably in the range of 10 to 100 µm, and preferably in the range of 20 to 50 µm. A glass having a flexibility (such as a flexible glass) is also applicable to the present invention with the thickness as above in the same manner as plastic film.

In the present invention, a plurality of electrodes are provided for connecting to the light receiving LSI chips, and the light emitting LSI chips are arranged along the length direction of the window part so as not to intersect the light transmitted through the window part. In this case, they may be provided only on one side of the window part, or a plurality of electrodes may be provided on both sides of the window part. As the material for constituting the electrode, a material having conductivity such as metal or conductive resin may be used. However, as the material of the electrode, a metal such as Au, Ag, Al, Ni, Cr, Cu and W, each used as a common material for the electrode, is preferred, and from the viewpoint of electrical properties, Cu is particularly preferred.

As a preferred further improved electrode, there is a laminated product composed of a first metal layer and a second metal layer. In the electrode of the laminated structure, the first metal layer provides the main electrode and the second metal layer provides the part for use in press bonding or heat bonding of electronic parts such as light receiving LSI chips. As further preferable examples, there are laminated electrodes such as those having a first metal layer made into a low-reflective layer, a second metal layer made into a low-reflective layer, a first metal layer on the surface on which a low-reflective layer is provided, and first and second layers, respectively, low-reflective layers being provided on the surface of both layers. A low-reflective layer will be described below.

As a manufacturing method of the electrode or the metal layer constituting the electrode of the present invention, there are various methods, namely: (1) Forming a thin metal film made of, for example, copper on the transparent substrate by a vacuum processing method such as sputtering or a vacuum deposition method. Electroplating or electroless plating is used as needed to increase the thickness of the previously prepared metal film or to laminate another metal on the thin metal film. (2) Providing a metal layer directly on the transparent substrate by electroless plating to prepare an electrode. (3) Producing an electrode by applying conductive ink directly on the transparent substrate. (4) Forming an electrode by bonding a metal foil made of, for example, copper on the transparent substrate with an adhesive. (5) Casting the transparent resin on the foil made of, for example, copper. (6) Forming an electrode by providing a conductive resin on the transparent substrate by printing or by a similar method therefor.

When a metal electrode or a metal layer is formed by a deposition process under a reduced pressure or in a vacuum, it is preferable to use a manufacturing process using an ion technique such as a sputtering process, an ion plating process, an ion cluster beam process, an ionized evaporation process or an ion-assisted evaporation process in order to increase the degree of contact between the metal electrode and the transparent substrate or between the metal layer and the transparent substrate. In order to increase the degree of contact between the metal electrode and the transparent substrate or between the metal layer and the transparent substrate, an intermediate layer may be provided between the metal electrode and the transparent substrate or between the metal layer and the transparent substrate. As the intermediate layer, any material that can increase the contact strength may be used, for example, there is a metal or a metal compound including, for example, Ni, Cr or plastic.

In the present invention, as a method for forming a metal electrode on the first main surface of the transparent substrate, a method for forming a metal electrode having a predetermined size on the first main surface using a mask or the like, or a method for forming a metal film on the entire first main surface and then applying etching to form a metal pattern of a predetermined size is used. A method for processing and forming a pattern of the metal electrode will be described in more detail. There are the following methods: (1) By using a resist or a mask, first, the part of the first main surface which is not the part of a metal electrode is covered, and then the metal electrode having a predetermined circuit pattern is directly formed, and after forming the pattern, removing the resist and the mask. (2) On the metal film formed on the entire area of the first main surface, forming a pre-defined circuit pattern. (3) On the metal film formed on the entire area of the first main surface, forming a mask with a resist covering a part of the metal film except the metal electrode area. Then increasing the thickness of the metal film by electroplating to prepare the metal electrode of a predetermined pattern. Then removing the resist and applying flash etching to further remove the unnecessary metal film while keeping the metal electrode part on the metal film.

When the metal electrode is of a laminated structure consisting of first and second metal layers, there are processing and forming methods with respect to the patterns of the metal electrodes, specifically as follows: (1) On the first metal electrode formed on the entire area of the first main surface, forming a predetermined pattern of the metal electrode with a resist for coating the first metal layer, then processing the unnecessary part of the first metal layer by etching and then removing the resist. It is acceptable to form a second metal layer on the first metal layer. (2) On the first metal layer, forming on the entire area of the first main surface a mask such that a resist covers the part of the metal film excluding the metal electrode surface. Then increasing the thickness of the metal layer by electroplating, electroless plating or laminating another metal on the metal layer to prepare the metal electrode having a predetermined pattern. Then removing the resist and applying flash etching to further remove unnecessary parts of the first metal layer while maintaining the metal electrode area remaining on the metal layer. If necessary, it is permitted to deposit a second metal layer on the upper metal electrode, then removing a resist and further applying flash etching to remove unnecessary metal film while keeping the metal electrode part, thereby forming a metal electrode pattern having a second metal layer. (3) On the first metal layer formed on the entire area of the first main surface, forming a mask such as a resist covering the part of the metal film except the metal electrode area having a predetermined pattern. Then, after forming a second metal layer, removing a resist and further applying flash etching thereto, forming the metal electrode by removing the part other than the metal electrode part. (4) Forming a metal film on a laminated structure consisting of first and second metal layers on the entire area of the first main surface, then forming a mask with, for example, a resist on the second metal layer covered with the metal electrode part of a predetermined pattern, then applying etching thereto to remove the metal layer except the metal electrode, and further removing the resist to form the metal electrode. (5) It is practical to form metal layers consisting of a low-reflective layer, a first metal layer, and a second metal layer on the entire area of the first and second main surfaces, then forming a mask with, for example, a resist on the second metal layer on an area of a predetermined pattern, then applying etching, removing the resist to form patterns of a plurality of metal electrodes, a plurality of aggregated electrodes, a darkening layer, and an antistatic layer.

When the electrode according to the invention is made of a laminated structure consisting of a first and a second metal layer, it is preferred that the second metal layer is comprised as described above, to which the electrical parts are attached by press bonding or hot bonding. The second metal layer of this type may be formed by vacuum methods such as sputtering methods, but preferably it is formed by gold plating, solder plating or printing. For example, when a gold plating layer is used as the second metal layer, this gold plating layer can be formed by various methods as follows: (1) An electroplating method in an alkane cyanide bath. (2) An electroplating method in a neutral or weak alkaline bath. (3) An ordinary gold plating method, for example, in a weak acid bath using an organic acid. A suitable thickness of the gold plating layer is usually in the range of 0.05 µm to 80 µm, preferably in the range of 0.1 µm to 50 µm, more preferably in the range of 0.5 µm to 50 µm, particularly preferably in the range of 0.1 µm to 5 µm.

When a solder plating layer is used as the second metal layer, this solder plating layer can be formed by some methods as follows, that is, (1) an electroplating method such as a fluoroboric acid bath, phenolsulfonate bath or alkanolsulfonate bath. (2) an electroless plating method such as substitution plating or reduction precipitation method. (3) a solder paste printing method in which solder paste such as solder cream is printed by a screen printing method. The thickness of the solder plating layer is usually in the range of 0.05 µm to 80 µm, preferably in the range of 0.5 µm to 50 µm, particularly in the range of 2 µm to 10 µm. In the present invention, solder means a metal or alloy having a low melting point used for bonding materials. This type of metal or alloy has a melting point, in particular of less than 723 K absolute temperature, including, for example, a simple substance or alloy of In, Sn, Pb or Zn. The solder metal used is usually a Sn-Pb alloy which forms a eutectic solder. In addition to the above, there are Homberg's alloy, Mellott's alloy, Newton's alloy, D'Arcet's metal, Lichtenberg's alloy, Crose's alloy, Rose metal, Wood's metal, Lipowitz metal, low melting point solder, alkali-proof solder, eutectic solder, JIS (Japanese Industrial Standard) solder, low thermoelectromotive force solder and aluminum solder or the like. In addition, alloys other than the above alloys but suitable for joining may be used as the second metal layer.

When forming a solder layer by a plating method or a printing method without using a molten solder bath having a relatively high temperature, the second metal layer can be formed with high reliability even when a plastic film having relatively low thermal resistance is used as the transparent substrate, let alone in the case where a substrate having high thermal resistance is used as the transparent substrate. Consequently, an electrical connection between the semiconductor device such as a light-receiving LSI chip and an electrode can be carried out by a method with high connection reliability using the solder.

In the optical circuit board of the present invention, a plurality of aggregated electrodes are arranged on the second main surface. In this specification, a common electrode on the second main surface is referred to as an "aggregated electrode". This aggregated electrode is used for passing signal or data between optical devices such as light receiving LSI chips or light emitting LSI chips and another circuit board or other electronic circuit, and for connecting these optical devices electrically equivalently in a connection arrangement such as a matrix connection. Each aggregated electrode is referred to as a common electrode for a variety of optical devices. The material and the manufacturing method with respect to the above electrode, particularly the metal electrode, are applied without changing the material and the manufacturing method of the aggregated electrode. The electrode on the first main surface and the aggregated electrode are connected by an electrical connection part penetrating the transparent substrate. The electrical connection part will be described below.

The electrical connection between an aggregated electrode and another circuit board or electric circuit may be formed by connecting one end of a connecting wire to the aggregated electrode, but it is preferable to make an external connecting terminal electrically connected to the aggregated electrode and one end of the connecting wire to this external connecting terminal. In addition, it is possible to use the external connecting terminal as a pad for direct bonding to a terminal provided on the external circuit board. The external connecting terminal may be provided on any of the first and second main surfaces. When the external connecting terminal is provided on the first main surface, it may be of the same structure as the electrode for the optical LSI chip and may be connected to the aggregated electrode through the electrical connection part penetrating the transparent substrate. On the other hand, when the external connecting terminal is provided on the second main surface, it may be formed as a pad connected to the aggregated electrode. By providing the external connection terminal, a heat-affected zone which absorbs the heat generated by the electrical connection between the external circuit and the optical circuit board can be limited in the vicinity of the external connection terminal, thereby preventing the propagation of thermal Heat is prevented across the entire circuit board. Therefore, high temperature solder can be used for joining even when a transparent substrate with low heat resistance is used.

In addition, with respect to electrodes that are a part of a plurality of electrodes formed on the first main surface, they can be usually connected to a common electrode (in this specification, a common electrode on the first main surface is referred to as a common electrode), provided that the first main surface is connected without connection to the aggregated electrode provided on the second main surface. The structure of this common electrode is similar to the aggregated electrode except that it is provided on the first main surface. The electrodes for optical devices and the common electrode are connected by a circuit pattern formed on the first main surface. It is also possible to form an external connection terminal at the end of the common terminal. The electrode, the common electrode and a circuit pattern for connecting them can be formed in the same manner on the first main surface.

An electrical connection part used for electrically connecting the electrode or the external connection terminal on the second main surface is described below. The manufacturing methods of the electrical connection part are, for example: (1) A penetrating hole is formed in the transparent substrate by machining the substrate using a drill or laser, and then the coating of the hole with a metal film formed in the hole is produced by applying electroless plating for complete electrical connection. The electrodes or the external connection terminal on the first main surface and the aggregated electrode are electrically connected with this electrical electrical connection part. (2) A penetrating hole is formed in the transparent substrate using a solution such as an acid, an alkaline or an organic solvent, and then electroless plating is applied to the hole to coat the inside of the hole with a metal film to complete the electrical connection part. Between the electrode or the external connection terminal and the aggregated electrode, they are connected with this metal film. (3) Applying a mechanical force such as compressing the electrode on the first main surface and the aggregated electrode on the second main surface both from the outside and simultaneously applying heat to electrically connect both electrodes. (4) As in the case of (3) above, applying a mechanical force between two electrodes and electrically connecting them. (5) As in the case of (3) above, applying a mechanical force between both electrodes and simultaneously applying a voltage between both electrodes to electrically connect them by applying Joule heat (resistance welding). And further (6) forming a through hole in the transparent substrate by machining with a drill or a laser and filling conductive resin or conductive paste into the hole to provide electrical connection. In the case of (6), the electrode or the external connection terminal on the first main surface and the aggregated electrode on the second main surface may be electrically connected by conductive resin or conductive paste. At this time, the conductivity of such conductive paste is improved by baking, along with the connection strength of the paste being also increased.

In the present invention, a low-reflective layer can be provided when the electrode or the aggregated electrode is assembled with a metal to protect against multiple reflection of light due to reflection on the surface of the metal. The low reflection layer may serve as the electrode in parallel or may be provided between the electrode and the transparent substrate. When the electrode is of laminated structure consisting of first and second metal layers, low reflection layer may serve as the first metal layer or the second metal layer, or may be provided between the first metal layer and the transparent substrate, or may be further provided on the second metal layer.

The visible light reflectance of the low-reflection layer is expected to be not more than 50%, but preferably not more than 10%, and particularly not more than 5%. As materials suitable for constituting the low-reflection layer, there are, for example, metals such as Ge, Si, Sn, W and solder; oxides of e.g. Cr, Cu, Fe, In, Mn, Ni, Pb, Pd, Pt, Ti, V and W; carbides of e.g. B, W; nitrides of e.g. Cr, Zr; sulfides of e.g. Ni, Pb, Pd and Cu and a phosphorus compound of e.g. Fe and the mixture thereof. In addition, it is possible to use a metal or a metal compound whose surface reflectance is reduced by applying a blackening treatment or an unevenness treatment and also a combination of the above treatments. Herein, blackening treatment means the treatment in which the metal surface is treated to form a layer having low light reflectance. As the method of blackening, there is, for example, a method using a commercially available black dye such as Ebonol manufactured by Mertech Inc. or a method of forming the layer of metal oxide or metal sulfide on the metal layer according to the method disclosed in Japanese Patent Application Laid-Open No. 41378/82 (JP-A-57-41378) and 47375/88 (JP-A-63-47375). In addition, it is acceptable to use setting type resin including carbon black or a color pigment as a resist used for forming the metal electrode. and this setting type resin can also be used as a low-reflective layer without removing it even after the etching treatment for patterning the metal electrodes is completed.

In the present invention, it is preferable to provide a darkening layer for controlling the light so that it does not penetrate the transparent substrate through a part other than the window part. The darkening layer defines the window part formed on the transparent substrate along the window part and covers the part other than the window part. When the darkening layer is additionally formed on the electrode formed as a pattern for connecting devices such as light-receiving LSI chips or wiring, the darkening effect is further increased. This darkening layer may be provided on any of the first and second main surfaces. However, when it is provided on the second main surface as described later, the antistatic layer should also have the function of the darkening layer combined with its own function, and it is not preferable to provide a single darkening layer. With regard to the light used for reading or image formation, the allowable light transmittance of the shading layer should be not more than 50%, preferably not more than 10%, and is most preferably not more than 5%. The low-reflectivity layer may be provided between the shading layer and the transparent substrate for the purpose of preventing multi-path reflection. This low-reflectivity layer is of the same nature as the above-mentioned low-reflectivity layer provided on the electrode and can be formed in the same manner as above.

A method for producing a shading layer is as follows: (1) Laminating a low reflectance layer made of, for example, a black chromium-plated metal layer or oxidized copper in a metal layer to prepare a shading layer. (2) dispersing a conductive filler comprising carbon black and/or metal particles such as platinum black in a resin matrix to form a layer constituting the shading layer. (3) preparing a film by dispersing such as a pigment or a dye in a resin to prepare a shading layer. (4) laminating resin having light absorption property such as polythiophene on the transparent substrate to form a shading layer.

The allowable thickness of the darkening layer is normally in the range of 0.05 µm to 50 µm, preferably in the range of 1 µm to 10 µm, and desirably in the range of 2 µm to 5 µm.

As described below, when the antistatic layer is formed on the second main surface side, a shading layer is formed on the first main surface opposite to the antistatic layer. Thus, the shading layer cooperates with the antistatic layer to prevent improper light from entering the window region more effectively, the improper light not being the practical light for reading or writing. In this case, the shading layer must be formed so as not to affect the electric signal generated at the time of reading a manuscript or the light going to a photosensitive material at the time of image formation, and thus it is preferable to form the shading layer with the resin containing a low-conductive pigment or dye. The shading layer on the first main surface and the antistatic layer on the second main surface together define the window region for use for only passing the light for reading a manuscript or the light for image formation. The window area that is to be defined as the clear area of the darkening layer kidneys usually has a straight slot shape, the slot width normally being in the range of 0.1 mm to 50 mm, preferably in the range of 0.3 mm to 2 mm.

In the present invention, the antistatic layer for preventing the optical circuit board from being charged may be provided on the second main surface. Particularly, when the circuit board is used in a contact type image sensor or the like in which the circuit board is rubbed together with a manuscript or a photosensitive matter, it is desirable to provide an antistatic layer for controlling the state charged by static friction. When the antistatic layer is provided, it is desirable that it be provided with the structure for preventing the circuit board from being charged, having light-shielding properties, thereby cooperating with the darkening layer for defining the window part. The allowable light transmittance of this type of antistatic layer for the wavelength of light for reading or writing is not more than 50%, but preferably not more than 10%, and further desirably not more than 5%. It is acceptable to provide a low reflectance layer of the same as mentioned above between the transparent substrate and the antistatic layer.

In order to define the window part, it is desirable that the antistatic layer has a shape including a slit-shaped opening corresponding to the window part. The opening usually has a straight shape and the width of the slit is normally in the range of 0.1 mm to 50 mm, preferably in the range of 0.3 mm to 2 mm. The thickness of the antistatic layer is generally in the range of 0.05 µm to 50 µm, preferably in the range of 1 µm to 10 µm, and the best is in the range of 2 µm to 5 µm.

The opening provided in the antistatic layer is preferably sized to correspond to an area between the electrode and the darkening layer formed on the first main surface of the transparent substrate. The width of the antistatic layer itself is not limited, but is preferably equal to or more than the width of the slit of the window part. Specifically, the width of the antistatic layer is preferably twice the width of the window part, and a more desirable value is about five times thereof. The width of the antistatic layer may be provided equally on both sides of the window, but in order to reduce the influence of the electrostatic charge on the LSI chips such as the light-receiving LSI chips, it is preferable to make the width larger on the side corresponding to the device. More specifically, the width of the antistatic layer with respect to the window on the side corresponding to the LSI chip is in the range of 2 mm to 100 mm, preferably in the range of 3 mm to 10 mm.

As a method for forming the antistatic layer on the second main surface of the transparent substrate, there are some methods as follows: (1) forming an antistatic layer by applying plating such as black chrome plating or black chromating treatment to the second main surface; (2) forming an antistatic layer by dispersing conductive fillers such as carbon black and/or metal particles (i.e., platinum black) in a resin matrix and then printing and curing it; (3) forming an antistatic layer by forming a metal layer or a metal layer having a low reflection layer and then etching the same.

In addition, when the transparent substrate to be used has high heat resistance, the antistatic layer can be formed by a general method using techniques such as plating, evaporation, thermal spraying, heating after coating or the like. When the resin with poor heat resistance such as PET, polycarbonate, PES is used, in order to In order to avoid deformation of the transparent substrate due to heat generated at the time of forming the antistatic layer, the temperature of forming the antistatic layer is preferably not more than 150°C, more preferably not more than 120°C, most desirably not more than 100°C. Higher forming temperatures may also be applicable in some cases.

As a method for producing the antistatic layer at the relatively low temperature, there are some methods, for example: (1) dispersing a conductive filler such as carbon black in advance in a one-component curing epoxy resin to print this resin in a mold having an opening, and then heating this resin to a predetermined temperature and curing to produce an antistatic film. This one-component type curing epoxy resin includes microcapsules which, dispersed therein, decompose at a predetermined temperature, the microcapsule comprising a catalyst for reacting with the base resin to produce the curing reaction. (2) using the resin comprising a curing agent dispersed therein and decomposing it at a predetermined temperature to react with the base resin and cure by the reaction. Dispersing the conductive filler, such as carbon black, in the resin to print the resin into a mold containing an opening. Then heating this resin to a predetermined temperature and allowing it to cure to produce the antistatic film.

In order to increase the antistatic effect, it is possible to provide a grounding electrode in the antistatic layer for grounding this grounding electrode.

The material and the manufacturing method with respect to the electrode, in particular the metal electrode, are without changing the material and the manufacturing method of the aggregated electrode, the antistatic layer, the external connection terminal and the darkening layer which are arranged on the first main surface opposite to each other in the ratio to the metal electrodes.

In the present invention, a light guide may be provided on the second main surface of the transparent substrate for introducing the light from an object for the window part or light emitted from the window area of the object. Herein, object means a manuscript arranged in an optical reading device or a photosensitive material arranged in an optical image forming device. Any material having a function of condensing or guiding the light may be used as the light guide. As preferred light guides, there are lenses such as Selfoc™ lens or an optical fiber array composed of a plurality of glass fibers or bundled plastic optical fibers. The rod lens array or optical fiber array on the second main surface of the optical circuit board may be preferably used in the case of a circuit board without the antistatic layer.

The optical circuit board of the present invention having the structure as described above can perform its function satisfactorily without aid or modification; however, in order to prolong the service life of the product using this optical circuit board, it is desirable to provide a protective layer on the outermost surface of the second main surface for increasing the friction tolerance thereof. The protective layer is formed by adhering a glass plate to the second main surface or by coating such as with a UV-curing type acrylic resin, silicone resin coating agent or silica sol agent. It is desirable to form this protective layer particularly in such a manner that the protective layer completely covers the antistatic layer. The thickness of the protective layer is in the range of 1 µm to 200 µm, preferably in the range of 2 µm to 100 µm, more preferably in the range of 5 µm to 20 µm.

Furthermore, in order to increase the durability of the electrical connections between the optical circuit board of the present invention and the optical LSI chips arranged on the circuit board, it is practical to cover the entire LSI chips or fill the area between the optical circuit board and the optical LSI chips by using setting or curing type resin. As the setting type resin, there are UV-curing resins, represented by pre-curing acrylic-based resins, the thermosetting resin is represented by, for example, silicone acrylate, room temperature curing epoxy-based resin and the mixture of the above.

The above and other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of preferred embodiments of the present invention.

Short description of the drawings:

Fig. 1 is a typical cross section showing an example of the structure of a common image sensor.

Fig. 2 is a cross-sectional view generally showing an optical circuit board according to the present invention used as an image sensor.

Fig. 3A is an oblique view showing an optical circuit board according to the first embodiment of the present invention.

Figs. 3B and 3C are plan views showing an example of the arrangement of an antistatic layer of a first embodiment.

Fig. 3D is a typical cross section taken along line A-A' of Fig. 3A.

Fig. 3E is a typical top view of an optical circuit board shown in Fig. 3A.

Fig. 3F is a typical cross-sectional view taken along line BB'of Fig. 3E.

Fig. 3G is an oblique view showing an example of another arrangement of external connection leads of a first embodiment.

Fig. 4 is a plan view generally showing an optical circuit board according to a second embodiment of the present invention.

Fig. 5A is a plan view generally showing an optical circuit board of a third embodiment of the present invention.

Fig. 5B is a typical cross section taken along line C-C' of Fig. 5A.

Fig. 6 is a typical cross section showing the structure of the optical circuit board according to Example 1.

Fig. 7 is a typical cross section showing the structure of the optical circuit board of Examples 2, 4 and 5.

Fig. 8 is a typical cross-sectional view showing the structure of an optical circuit board according to Example 3.

Fig. 9 is a typical cross section showing the structure of an optical circuit board according to Example 6.

Fig. 10 is a typical cross-sectional view showing the structure of an optical circuit board according to Examples 7, 8, 10 and 11.

Fig. 11 is a typical cross-sectional view showing the structure of an optical circuit board according to Example 9.

Fig. 12 is a typical cross section showing the structure of an optical circuit board of Examples 12 and 13.

Fig. 13 is a typical cross section showing the structure of an optical circuit board according to Example 14.

Fig. 14 is a typical cross-sectional view showing the structure of an optical circuit board according to Examples 15 and 16.

Fig. 15 is a typical cross section showing the structure of an optical circuit board according to Example 17.

Fig. 16 is a typical cross-sectional view showing the structure of an optical circuit board according to Example 18.

Fig. 17 is a typical cross-sectional view showing the structure of an optical circuit board according to Example 19.

Fig. 18 is a typical cross-sectional view showing the structure of an optical circuit board according to Example 20.

Fig. 19 is a typical cross-sectional view showing the structure of an optical circuit board according to Example 21.

Fig. 20 is a typical cross-sectional view showing the structure of an optical circuit board according to Example 22.

Fig. 21 is a typical cross-sectional view showing the structure of an optical circuit board according to Examples 23 and 25.

Fig. 22 is a typical cross-sectional view showing the structure of an optical circuit board according to Example 26.

Fig. 23 is a typical cross section showing the structure of an optical circuit board according to Example 28.

Description of the preferred embodiments:

The present invention will be described in more detail below with reference to the drawings.

The optical circuit board of the present invention can be used as described above by constructing an image sensor of an optical reading device by mounting a light receiving LSI chip or as a recording head of an optical image forming device such as a photo-printing device by mounting a light emitting LSI chip. The optical circuit board of the present invention used as an image sensor of the optical reading device will be described first with reference to Fig. 2.

The optical circuit board according to the invention is basically constructed using a film-like transparent substrate 1 having a slit-shaped window part 7 arranged so that the light can pass only through this window part. The circuit board further comprises a plurality of metal electrodes 2 for connection with the light receiving LSI chips 13 arranged on the first main surface along the window part 7, a plurality of aggregated electrodes 3 arranged on the second main surface opposite to the first main surface in the transparent substrate 1 arranged in Longitudinally extending along window portion 7, the aggregated electrode 3 and the metal electrode 2 are electrically connected to a connecting portion 26 penetrating through the transparent substrate 1, and the metal electrodes 2 are arranged in a manner not to prevent the transmission of light through the window portion. In Fig. 2, the direction of arrangement of the metal electrodes 2, that is, the longitudinal direction of the window portion 7 or the aggregated electrodes 3, is perpendicular to the surface including the figure. The aggregated electrodes 3 are arranged corresponding to the deposition area of the metal electrodes 2.

Furthermore, the optical circuit board includes a darkening layer 5 defining a window portion 7 and is disposed on the first main surface opposite to the metal electrodes 2 disposed between the window portion 7. The darkening layer 5 also extends in the longitudinal direction of the window portion 7 and a slit-shaped opening between the darkening layer 5 and each metal electrode 2 practically constitutes an exposed area of the window portion 7 on the first main surface. It is preferable to provide the darkening layer also on the space between each metal electrode. The darkening layer provided on the space between each metal electrode must be made of a material having a good insulating property. The second main surface includes an antistatic layer 6 having good conductivity and good darkening properties. The antistatic layer 6 has a slit-shaped opening corresponding to the window portion 7. The antistatic layer 6 prevents the circuit board from charging, for example by frictional static, and at the same time serves to define the window portion 7 on the second main surface. A transparent protective layer 8 is provided in such a way that the second main surface, which includes the antistatic layer 6 and the aggregated electrode 3 applied thereto, is covered. Lenses, including SelfocTM lenses, can also be used here. or a light guide, such as a fiber optic array that guides the light, may be used instead of the antistatic layer.

When the optical circuit board is used in an optical reading device in which image data of an image is input by the relative movement of a manuscript and an image sensor, the optical circuit board is arranged in the optical reading device in such a manner that the longitudinal direction of the window part 7 moves across the direction of movement of the manuscript 14 while the second main surface faces the manuscript 14. In this case, the light from the light source 12 for reading the manuscript is introduced into the transparent substrate 1 from the first main surface side and passed through the window part 7 to irradiate the manuscript 14, then reflected according to the image pattern on the manuscript and again passed through the window part 7 to enter the light receiving LSI chip 13 connected to the metal electrode 2. The light receiving LSI chip 13 and the metal electrode 2 are connected to each other by bump 13a of LSI chip 13. The manuscript 14 is moved in the right-left direction of the figure by a transport roller 60.

When the optical circuit board of the present invention is used in the optical device for forming an image such as a photo printer, the light emitting LSI chip may be attached to the electrode 2 with its light emitting surface facing the window part 7 instead of the light receiving LSI chip 13, and the second main surface of the transparent substrate may be arranged opposite to the photosensitive surface of the photosensitive object. In addition to the above-mentioned manuscript movement type, it is possible to use any system in which the photosensitive object or the optical circuit board itself is moved. These movement systems only show the relative relationship between between the objects and are theoretically equivalent to each other.

The optical circuit board according to the invention is further described with reference to the embodiments. Fig. 3A shows an optical circuit board of a first embodiment.

In Fig. 3A, on the first main surface (upper surface of the figure) of the film-like transparent substrate 1, a darkening layer 5 is provided on one side and a plurality of metal electrodes 2 are provided on the other side, which are arranged between a layer which is a slit-shaped window part 7. This darkening layer 5 and the metal electrode 2 together define the area of the window part 7. Each metal electrode 2 having a shape of a strip of paper is arranged with its longitudinal direction perpendicular to the longitudinal direction of the window part 7. When this optical circuit board is used for the optical reading device, the optical circuit board is mounted on the optical reading device so that the longitudinal direction of the window part 7 is transverse to the direction of relative movement of the manuscript and the circuit board.

While on the second main surface (lower surface of the figure) of the transparent substrate, that is, on the main surface opposite to the first main surface, a plurality of the aggregated electrodes 3 are arranged so as to be disposed in parallel relation with the surface of the first main surface on which the metal electrodes 2 are provided. Each aggregated electrode 3 has a long, ribbon-like shape longer than the long side of the window part 7. In addition, on the second main surface, an antistatic layer 6 composed of a material having light-shielding properties and electrical conductivity is provided. As shown in Fig. 3B, the antistatic layer 6 is in the shape of a rectangle with an opening made by cutting the area corresponding to the window part 7; that is, in a shape composed of the sides of rectangles. Furthermore, as shown in Fig. 3C, the antistatic layer 6 may be provided as two tape-like layers arranged on both sides of the window part 7. A transparent protective layer 8 is provided in such a manner as to cover the entire area of the second main surface, the aggregated electrodes 3 and the antistatic layer 6.

The positional relationship will now be described with reference to the metal electrode 2 and the darkening layer 5, both on the first main surface, and the antistatic layer 6 on the second main surface. These items essentially define the area of the window part 7. However, the edge of the metal electrode 2 and the darkening layer 5 may be positioned coincident with the edge of the opening of the antistatic layer 6, or may protrude a little beyond the edge in the opening of the antistatic layer 6, as long as they do not prevent the light from passing through the window part 7. With respect to the size of the area to be fixed as the window part 7 on the first main surface, that is, the size of the area enclosed by the metal electrode 2 and the darkening layer 5, and the size of the opening of the antistatic layer 6, they may be different insofar as the common area for the light to pass through is formed.

With respect to the first main surface, it is noted that the external connection leads 30 of the same number as the number of the aggregated electrodes 3 are mounted on the surface corresponding to one end of the aggregated electrode 3; together they constitute the periphery of the optical circuit board. Each of the external connection leads 30 has a pad-like shape used for connection to the external circuit and connected to the aggregated electrode 3 through an electrical connector. ing part 20 is electrically connected 1:1, which is provided so that it penetrates through the transparent substrate 1.

Each metal electrode 2 can be electrically connected to each aggregated electrode 30 through the electrical connection portions 20. A cross-sectional view shown in Fig. 3D explains how the two electrodes are connected through the electrical connection portion 20. Fig. 3D also explains a light source 12 and a light receiving LSI chip 13 as an image sensor. The light receiving LSI chip 13 and the electrode 2 are connected to each other through a lead wire 13a provided in the light receiving LSI chip 13. Each electrode 2 can optionally select the aggregated electrode 3 as a connection partner; insofar as the aggregated electrode 3 is provided for matrix connection as for light receiving devices, one skilled in the art can easily find out the type of combination is desired with respect to combination of connection of the metal electrode 2 and the aggregated electrode 3. In addition, it is possible to connect the electrodes 2 to the aggregated electrodes 3 in a manner that any one of the light-receiving LSI chips 13 can be selected by selecting two aggregated electrodes 3. Fig. 3E generally explains the positional relationship between each metal electrode 2 and each aggregated electrode 3 as viewed from the first main surface side. In this figure, each part where the metal electrode 2 and the aggregated electrode 3 are shown overlapping and enclosed with thick lines represents the position where the metal electrode 2 and the aggregated electrode 3 are practically connected. Also in this figure, it is explained that the metal electrodes 2 are in pairs, and on the side of the window part 7, the top of each electrode of the pair has a symmetrical shape with each other for easy mounting of the light-receiving LSI chip or the light-emitting LSI chip. Fig. 3F is a typical cross section, corresponding to Fig. 3E.

Although the first embodiment has been described above, there are various kinds of modifications. In the optical circuit board shown in Fig. 3E, the external connection leads 30 are arranged as a group on the opposite side of the window portion 7, opposite to the metal electrode 2 interposed therebetween. In this case, by changing the shape of the aggregated electrode 3 on the second main surface to a shape of a letter L, the aggregated electrode 3 and the external connection terminal 30 can be connected to an electrical connection part 20 passing through the transparent substrate layer 1.

If the antistatic layer 6 can provide a sufficient light-darkening effect, it is possible to construct the circuit board without providing the darkening layer on the first main surface.

With respect to the light-receiving LSI chip or the light-emitting LSI chip, it is permissible to use an LSI chip having a plurality of terminals or to use an LSI chip of a long-format array type having a plurality of electronic devices mounted thereon. On the other hand, in the case where an array type LSI chip is used, metal electrodes for LSI chips are allocated in the number of terminal leads provided in the LSI chips and used for electrical and mechanical transport. In the optical circuit board of the present invention, since the number of metal electrodes can be arranged along the window, it can suitably increase the mechanical support points with respect to the array type LSI chip.

Fig. 4 is a plan view generally showing the relationship between the metal electrode and aggregate electrode in the optical circuit board of the second embodiment of the present invention. This circuit board is almost similar to that of the first embodiment, but some of the metal electrodes on the first main surface, represented by reference numeral 2a, is not connected to the aggregated electrode 3, but instead the metal electrodes 2a are electrically connected to a common electrode 36 through a circuit pattern 35. The common electrode 36 serves as a substitute for an aggregated electrode. The common electrode 36 is provided on the first main surface on the opposite side of the window part 7 with each metal electrode 2, 2a interposed therebetween, having a band-like shape extending in the longitudinal direction of the window part 7. On the end part of the common electrode 36, an external connection terminal 30a is provided as a base surface for use in connection with an external circuit. This external connection terminal 30a has a structure similar to that of the external connection terminal 30 connected to the aggregated electrode 3. In the present invention, since the circuit pattern 35 and the common electrode 36 can be formed simultaneously with the metal electrode 2, 2a, there is practically no increase in man-hours for the preparation thereof. In addition, compared with the case where all the metal electrodes are connected to the aggregated electrodes, this embodiment can reduce the number of the electrical connection parts 20 penetrating through the transparent substrate 1.

An optical circuit board of a third embodiment of the present invention is shown in Figs. 5A and 5B. In Fig. 5B, a state of the optical circuit board with a light emitting LSI chip 16 mounted thereon is shown. In this embodiment, the metal electrodes 2 are mounted on the both sides of the window part 7 and thus, in the first main surface, the window part 7 is defined by metal electrodes 2 arranged on both sides thereof. Therefore, the darkening layer is not provided in this case. According to the area on each side of the window part where metal electrodes 2 are formed, aggregated electrodes 3 are naturally formed on the second main surface. In other words, this circuit board has an almost symmetrical structure with respect to the area longitudinally enclosing a center line of the window part 7 which is perpendicular to the surface of the transparent substrate 1.

This optical circuit board can mount the light emitting LSI chip 16 on the back of pairs of metal electrodes 2 disposed oppositely between the window portion 7. In this case, a light emitting surface 16a of the light emitting LSI chip 16 is disposed just above the window portion 7 opposite to the window portion 7, and the light emitting LSI chip 16 with its connection terminal 16b is thereby connected to the respective two metal electrodes disposed oppositely between the window portion 7. When the optical circuit board according to the present invention is applied to the optical image forming device, since the light passing through the window of the circuit board is only the emitted light emitted from the LSI chip mounted on the circuit board, the light emitting LSI chip can be disposed so as to cover the window portion of the present embodiment. When the light-emitting LSI chips are arranged in this manner and since they are supported at both ends thereof, the mechanical strength of the arrangement of the circuit board and the light-emitting LSI chips is increased. Even when the circuit board is applied to the optical reader by using an array type LSI chip in which the light-emitting LSI chip and the light-receiving LSI chips are fitted in the same package, it becomes possible to use a circuit board in which the LSI chip is fixed covering the window part.

The present invention will be described below with reference to practical examples.

Example 1:

An optical circuit board was manufactured as shown in Fig. 6. The circuit board is similar to that shown in the first embodiment, but differs in that a darkening layer, an antistatic layer and a protective layer are not provided. The metal electrode 2 has a light-receiving LSI chip 13 bonded thereto.

A PES film having a thickness of 50 µm was used as the transparent substrate 1, and on first and second main surfaces thereof, Cr (0.01 µm thick) and Cu (0.3 µm thick) were coated sequentially by a DC magnetron sputtering method to prepare a metal thin film. Then, a penetrating hole serving as an electrical connection part was formed in the transparent substrate 1 through a hole at the position where the metal electrode 2 and the aggregated electrode 3 were to be electrically connected. The resist ink was applied to the metal thin film covering the area where the metal electrode 2 and the aggregated electrode 3 were not formed, so that based on the position of this penetrating hole, the metal electrode 2 was formed on the first main surface and the aggregated electrode 3 was formed on the second main surface. The copper layer of about 0.3 µm thickness was deposited on the inner wall of the penetration hole by electroless plating and further the copper layer of about 5 µm thickness was provided on the inner wall of the penetration hole and an area of exposed metal thin film was electroplated. This copper layer became a first metal layer of the metal electrode.

Then, by plating in an alkanolsulfonate bath, a solder layer was formed on the first metal layer as a second metal layer composed of Sn-Pb alloy of about 5 µm thickness. Thereafter, the resist ink was removed, followed by removal of non- required metal. By the above process, the metal electrode 2 and the aggregated electrode 3 provided on the transparent substrate 1 were electrically connected to each other through the electrical connection part 20.

Thermosetting resin comprising silicone acrylate was applied to the first main surface and around the window part 7 and the metal electrode 2. A plurality of light-receiving LSI chips 13 having connecting leads 13a were arranged on the predetermined metal electrodes 2, then held at a temperature of 150°C for 5 minutes under the pressure of 1 kgf/cm2 to bond the light-receiving LSI chips 13 and the metal electrodes 2 while curing the resin. As a result, no cracks and separation were detected in the bonding part. The light from the light source 12 was passed through the window part 7 and irradiated a manuscript which was moved facing the second main surface. Then, the light reflected from the manuscript was detected by the light-receiving LSI chips 13 and read by an optical reader. As a result, the reading was carried out correctly.

Example 2:

An optical circuit board was manufactured as shown in Fig. 7. This circuit board is similar to that shown in the first embodiment, but the metal electrode 2 has a structure in which a first metal layer 2a and a second metal layer 2b are laid on the transparent substrate 1 in sequence. In addition, a darkening layer 5 is provided on the second metal layer 2b except for the area on which the light-receiving LSI chips 13 are mounted. The darkening layer 5 is also provided on the space between the adjacent metal electrodes 2 as a unit with the darkening layer 5 on the metal electrode 2.

A PEEK film of 50 µm thickness was used as transparent substrate 1 and deposited on a first and second main surface thereof, Cr (0.01 µm thick) and Cu (0.3 µm thick) were coated successively by a DC magnetron sputtering method to prepare a metal thin film. Then, resist ink was applied to the metal thin film covering the area where the metal electrode 2 and the aggregated electrode 3 were not formed, so that the metal electrode 2 and the aggregated electrode 3 were formed on the first and second main surfaces, respectively. A penetrating hole serving as an electrical connection part 20 was provided in the transparent substrate 1 with a drill at the position where the metal electrode 2 and the aggregated electrode 3 were to be electrically connected to each other. The copper layer of about 0.3 µm thick was deposited on the inner wall of the penetrating hole by electroless plating, and further, the copper layer of about 5 µm thick was provided on the inner wall of the hole and an area of exposed metal thin film by electroplating. This copper layer consisted of a first metal layer of aggregated electrode 3 and also a first metal layer 2a of metal electrode 2.

Then, a solder layer consisting of Sn-Pb alloy of about 5 µm thickness was formed on the copper layer by plating in an alkanol sulfonate bath. The second metal layer 2b of the metal electrode 2 was composed of this solder layer. Thereafter, the resist ink was removed, followed by removal of unnecessary metal. By the above operation, the metal electrode 2 and the aggregated electrode 3 were provided on the transparent substrate 1, electrically connected to each other by means of the electrical connecting part 20.

Subsequently, darkening layer 5 was formed on the first main surface by printing, heating and curing a thermosetting resin including a black pigment in a manner when the window part 7 was interposed. At this time, darkening layer 5 was formed on the metal electrode 2 and deposited on the space between each metal electrode 2. In addition, an antistatic layer 6 having a darkening property was provided on the second main surface so as to enclose the window portion by applying and curing a mixture of thermosetting resin with carbon black particles. The surface resistance of this antistatic layer 6 was 300 Ω/ and the light transmittance of the darkening layer 5 was 1% or less. Then, UV-curing urethane acrylic resin was applied and coated on the second main surface covering the aggregated electrode 3, the antistatic layer 6 and the window portion 7 to prepare a protective layer 8 of 10 µm thickness.

A plurality of light-receiving LSI chips 13 with connection leads were placed on the predetermined metal electrode 2, then held at a temperature of 150°C for 5 minutes under a pressure of 5 kgf/cm2 to bond the light-receiving LSI chips 13 and the metal electrodes 2. As a result, no cracks and separations were detected in the bonding part. The light from the light source 12 was passed through the window part 7 and irradiated a manuscript 14 which was moved facing the second main surface. Then, the light reflected from the manuscript 14 was detected by the light-receiving LSI chips 13 and read by an optical reader. As a result, it was confirmed that the reading was carried out correctly.

Example 3:

An optical circuit board was manufactured as shown in Fig. 8. This circuit board is similar to that shown in Fig. 7 of Example 2, but has a structure in which a darkening layer 5a is provided in the second main surface in a manner to enclose a window portion 7 and a transparent antistatic layer 6a is further provided so as to cover the darkening layer 5a and the window portion 7. ster part 7. A protective layer 8 is provided only above antistatic layer 6a, without including the area where aggregated electrode 3 is provided.

A PES film of 25 µm thick was used as the transparent substrate 1, and on a first and second main surface thereof, a Cu film of 0.3 µm thick was formed by a DC magnetron sputtering method. Then, in the same manner as in the above examples, the resist ink was applied to a metal thin film covering the area where a metal electrode 2 and the aggregated electrode 3 were not formed. A penetrating hole serving as an electrical connecting part 20 was formed in the transparent substrate 1 with a perforator at the position where the metal electrode 2 and an aggregated electrode 3 are to be electrically connected. The copper layer of about 0.3 µm thick was deposited on the inner wall of the penetrating hole by electroless plating to electrically connect the copper thin films on the first and second main surfaces to each other. In addition, the copper layer of about 5 µm thickness was provided by electroplating on the inner wall of the hole and an area with exposed thin copper film. This copper layer constituted a first metal layer of the aggregated electrode 3 and also a first metal layer 2a of the metal electrode 2.

Subsequently, after the resist was removed and the unnecessary thin copper film was removed one after another, a solder layer consisting of Sn-Pb alloy of about 2 µm in thickness was formed on the copper layer by a substitution plating method. A second metal layer 2b of the metal electrode 2 was composed of this solder. Thus, the metal electrode 2 and the aggregated electrode 3 were provided on the transparent substrate 1.

Subsequently, the darkening layer 5, 5a was applied to both the first and the second main surface by Printing, heating and curing the thermosetting resin enclosing a black pigment formed in such a manner as to interpose the window portion 7. The darkening layer 5 was formed on the metal electrode 2 and on the space between each metal electrode 2. The light transmittance of these darkening layers was 1% or less. In addition, a transparent and conductive antistatic layer 6 was provided on the second main surface side so as to cover both the window portion 7 and the darkening layer 5a by applying and curing the resin-enclosing particles of tin oxide. The surface resistance of this antistatic layer 6 was 500 Ω/ . Then, UV-curing urethane acrylic resin was applied and cured in such a manner as to cover the antistatic layer 6 to form a protective layer 8 of 10 µm in thickness.

Then, by holding the above circuit board at a temperature of 150°C for 30 seconds under the pressure of 5 kgf/cm², the light receiving LSI chip 13 and the metal electrode 2 were bonded together. As a result, no cracks and separations were detected in the bonding portion, and it was confirmed that the reading was correctly carried out as an optical reading sensor.

Example 4:

A printed circuit board was manufactured having the same structure as that shown in Fig. 7 of Example 2. On a first and second main surface of the transparent substrate 1 made of a Capton V film of 25 µm thickness, a thin copper film of 1 µm thickness was formed by an ion evaporation thin film forming method, and a penetrating hole serving as an electrical connection part was formed on the transparent substrate 1. Then, the resist ink was applied to the thin copper film covering the area where a metal electrode 2 and an aggregated electrode 3 were not formed. The copper layer of about 0.3 µm thick was deposited on the inner wall of the penetration hole by electroless plating, and the copper layer of about 10 µm thick was provided by electroplating on the inner wall of the hole and an area with an exposed thin copper film. This copper layer constituted the aggregated electrode 3 and also a first metal layer 2a of the metal electrode 2. After a nickel layer of 1 µm thick was formed on the copper layer (first metal layer 2a) on the first main surface side, a gold layer of 1 µm thick was provided by gold plating to form a second metal layer 2b on the metal electrode 2. Thus, the metal electrode 2 and the aggregated electrode 3 were connected by an electrical connection part 20 provided on the transparent substrate 1.

Then, the darkening layer 5 was formed on the first main surface by printing and curing the UV-curing colored resin Raycure 4200 (Jujo Kako Inc.) so that the window part 7 is defined. Furthermore, on the second main surface side, the thermosetting resin (Misui Toatsu Chemicals Inc.; Structbond 920) including carbon black particles was applied so that the window part 7 is defined and heat-cured, thus forming an antistatic layer 6 having a light darkening property. The surface resistance of this antistatic layer 6 was 300 Ω/ and its light transmittance was 1% or less. Then, UV-curing urethane acrylic resin was applied and cured on the second main surface in a manner that it covered the aggregated electrode 3, the antistatic layer 6 and the window part 7 to prepare a protective layer 8 of 10 µm thickness.

By press-bonding light-receiving LSI chips 13 with Al leads to metal electrode 2 at temperatures of 200ºC for 30 seconds, the light-receiving LSI chips 13 were fixed on the circuit board. As a result, there were no cracks and no separation on the bonded part. By After mounting the circuit board mounted with the light receiving LSI chips for the optical reader, it was tested. As a result, it was satisfactorily confirmed that the optical reader can read the data correctly.

Example 5:

A circuit board was manufactured having the same construction as shown in Fig. 7 of Embodiment 2, but no darkening layer was provided on a second metal layer of a metal electrode 2. A copper foil of 18 µm thick was first treated with a black coloring treatment applied to both surfaces thereof, and then a PES film of 10 µm thick was formed on one side thereof by a casting method. This PES film constituted a transparent substrate 1 and the copper foil surface constituted a second main surface of the transparent substrate 1. Subsequently, a thin copper layer of 0.3 µm thick was formed on a first main surface of the transparent substrate 1, that is, on the surface on which the copper foil was not provided, by means of a DC magnetron sputtering method.

Then, on both the first and second main surfaces, the resist ink was applied to the copper foil and the thin copper foil which is the surface other than the surface on which the metal electrode 2, an aggregated electrode 3 and a darkening layer 5 were formed. In addition, on the thin copper film on the first main surface, a solder layer consisting of Sn-Pb alloy of about 5 µm in thickness was provided by electroplating in an alkanolsulfonate bath. This solder layer constituted a second metal layer 2b of the metal electrode 2 and also a second layer of the darkening layer 5. By etching the copper foil on the second main surface side, the aggregated electrode 3 and an antistatic layer 6 were formed. In this case In example 5, the antistatic layer 6 was built up using a copper foil. The resist printing ink was then removed.

Subsequently, a heating electrode and a welding electrode were contacted at the position where the metal electrode 2 and the aggregated electrode 3 were electrically connected, thereby forming an electrical connection part 20 connecting between the main surfaces. Furthermore, a UV-curable urethane acrylic resin was applied and cured on the second main surface side in a manner that it covered the aggregated electrode 3, the antistatic layer 6 and a window part 7, thus forming a protective layer 8 of 15 µm in thickness.

The light receiving LSI chips 13 with leads and the metal electrodes 2 were connected by press bonding under the condition of 5 kgf/cm², 200ºC and 30 seconds. No cracks and separation were detected in the connection part. It was also confirmed that the optical reading device with the circuit board attached with the above device operated normally for reading.

Example 6:

A circuit board shown in Fig. 9 was manufactured. This circuit board had a structure including a lens provided by adhering a Selfoc™ lens (a rod lens array) 17 to the second main surface side of the transparent substrate 1 through an adhesive layer 9 of the circuit board illustrated in Fig. 6 of Example 1. In addition to that, a darkening layer 5 made of thermosetting resin including a black pigment was provided on the first main surface of the transparent substrate 1 so that the window part 7 was defined including the darkening layer 5 provided on the second metal layer 2b. For the adhesive layer 9, UV-curable acrylate resin was used. The lens 17 was positioned corresponding to the window part 7. After mounting a plurality of light-receiving LSI chips in A reading test was carried out in the manner shown in Fig. 1 and it was confirmed that the result was satisfactory.

Example 7:

An optical circuit board was manufactured as shown in Fig. 10. This circuit board was similar to that shown in the first embodiment, but provided without a protective layer thereon. A metal electrode 2, an aggregated electrode 3, a darkening layer 5 and an antistatic layer 6 each had a laminated structure of two metal layers, and a low-reflective layer 4 having low light reflectance was disposed between the lower metal layer and the transparent substrate 1.

A PES film of 50 µm thick was used as a transparent substrate 1, and on first and second main surfaces thereof, a black nickel oxide layer of 0.1 µm thick was formed as a low reflection layer 4 by a DC magnetron sputtering method, followed by a thin copper film of 0.5 µm thick formed on the above-mentioned lower reflection layer 4 by the same method.

Then, a mask was placed over the entire second main surface for protection. A resist resin was printed on the first main surface with a pattern corresponding to the metal electrode 2 and the darkening layer 5, and then a copper layer of 5 µm thick was formed by electroplating. The thin copper film and this copper layer constituted a first metal layer 2a. Then, a second metal layer 2b comprising a Sn-Pb alloy of about 5 µm thick was formed on the first metal layer by electroplating in an alkanolsulfonate bath. Thereafter, resist ink was removed, and then unnecessary nickel oxide and the thin copper film were removed therefrom by flash etching. By the above-mentioned operation, the metal electrode 2 and the darkening layer 5 were prepared in a manner for defining the window part 7. In addition, external connecting leads were formed along with the formation of the metal electrode 2.

Subsequently, a mask for protection was placed on the first main surface, the mask on the second main surface was removed, and the resist resin was printed on the second main surface on the area where the aggregated electrode 3 and the antistatic layer 6 were not formed. After that, the solder layer was formed by electroplating and the resist was removed, and then unnecessary nickel oxide and thin copper film were removed to prepare the aggregated electrode 3 and the antistatic layer 6 having a darkening property was provided for defining the window part 7. The aggregated electrode 3 had a first metal layer 3a on the transparent substrate 1 side thereof comprising a thin copper film, and a solder layer were stacked on the first metal layer 3a as a second metal layer 3b. The reflectance of the lower reflection layer 4 composed of the nickel oxide was 29%.

An electrical connection part 20 was formed by resistance welding, and thus the metal electrode 2 and the external connection terminal were electrically connected to the aggregated electrode 3, whereby the optical circuit board was completed.

Light receiving LSI chips 13 for reading, which had connection leads, were connected to the circuit board under the condition of 170°C held for 3 minutes, and in the same manner, the external connection terminal and an external driver circuit board were connected. In this case, no cracks and separation were detected in the connection parts. The light from the light source 12 was passed through the window part 7 and irradiated a manuscript 14 moved facing the second main surface. Detection of light reflection from the manuscript with the light receiving LSI chips 13; the light was detected with an optical reading device. The result confirmed that the reading activity was carried out appropriately.

Example 8:

A circuit board shown in Fig. 10 was manufactured in the same manner as in Example 7. However, with respect to the manufacturing process of a metal electrode 2 and a darkening layer 5 formed on a first main surface, the process of forming a copper layer by electroplating was omitted. Specifically, a first metal layer 2a of the metal electrode 2 composed of only a thin copper film was formed by a DC magnetron sputtering method.

Light receiving LSI chips 13 for reading with connection leads were connected to the thus prepared circuit board under the condition of 170°C held for 3 minutes, and in the same way, the external connection terminal and the external driver circuit board were connected. In this case, no cracks and separations were detected in the connection parts. The light from a light source 12 was passed through a window part 7 and irradiated a manuscript 14 which was moved facing the second main surface. Upon detecting the light reflected from the manuscript with the light receiving LSI chips 13; the light was read by an optical reading device. As a result, correct optical reading was confirmed.

Example 9:

An optical circuit board was manufactured as shown in Fig. 11. This circuit board is similar to that shown in Fig. 10, but differs from the circuit board shown in Fig. 10 in that an aggregated electrode 3 and an antistatic layer 6 are composed of only one copper foil, both surfaces of which are treated to be blackened, and furthermore a transparent protective layer 8 is formed on a second main surface. so that it covers a window part 7 and the antistatic layer 6.

A copper foil having a thickness of 18 µm was first treated with a black coloring treatment applied to both sides thereof, and then a PES film having a thickness of 10 µm was formed on one side thereof by a casting method. This PES film constituted a transparent substrate 1, and the copper foil-coated surface constituted the second main surface of the transparent substrate 1. Then, a black nickel oxide layer (low-reflective layer 4) of 0.1 µm thick and a thin copper layer of 0.3 µm thick were sequentially deposited on a first main surface of the transparent substrate 1 by a DC magnetron sputtering method. This thin copper film was a first metal layer 2a of the metal electrode 2.

Then, a mask for protection was placed over the entire copper area of the second main surface. A resist resin was printed on the first main surface with a pattern corresponding to the metal electrode 2 and the darkening layer 5. Then, a solder layer comprising Sn-Pb alloy of about 5 µm in thickness was formed on the thin copper layer by electroplating in an alkanolsulfonate bath. This solder layer was a second metal layer 2b of the metal electrode 2. Then, the resist ink was removed, and thereafter, the unnecessary nickel oxide and the thin copper foil were removed. By the above-mentioned operation, the metal electrode 2 and the darkening layer 5 were provided.

Subsequently, a mask for protection was placed on the first main surface and the mask on the second main surface was removed, then the resist resin was printed on the second main surface and the area where the aggregated electrode 3 and the antistatic layer 6 were not formed. After that, the copper foil was processed by etching and the resist was applied to form the aggregated Electrode 3 and the antistatic layer 6 having darkening property were removed. Since the aggregated electrode 3 and the antistatic layer 6 each consisted of a copper foil treated to be black colored on both sides thereof, the low reflection layer 4 was provided at the junction between the aggregated electrode 3 or the antistatic layer 6 and the transparent substrate 1, and on the surface of the substrate which was on the side of the manuscript 14.

Thereafter, a heating electrode and a welding electrode head were contacted to the position where the metal electrode 2 and the aggregated electrode 3 were connected to carry out resistance heating, thereby forming an electrical connection part 20 connecting between these electrodes. In addition, a UV-curable urethane acrylic resin was applied and cured on the second main surface side in a manner that it covered the window part 7 and the antistatic layer 6, thus forming a protective layer 8 of 25 µm in thickness.

Semiconductor light receiving LSI chips 13 with terminals and the metal electrodes 2 were connected by press and heated under the condition of 5 kgf/cm², 150ºC, held for 5 minutes. No cracks and separation were detected in the connection part. By performing the reading test, it was confirmed that reading was normally performed.

Example 10:

An optical circuit board was manufactured with the same structure as shown in Fig. 10 of Example 7. On a first and a second main surface of a transparent substrate 1 which was a uniaxially drawn PEEK film having a thickness of 25 µm, a low reflection layer 4 comprising a black nickel oxide having a thickness of 0.1 µm was formed by DC magnetron sputtering method and A thin copper film with a thickness of 0.5 μm is then formed.

On the first and second main surfaces, a predetermined pattern of resist resin was applied and a copper layer of 5 µm thick was deposited by electroplating. Then, the resist resin was removed and unnecessary thin copper films were removed by flash etching and a solder layer of about 1 µm thick was formed by a substitution solder plating method. By the above method, a metal electrode 2, an aggregated electrode 3, a darkening layer 5 and an antistatic layer 6 were formed. The metal electrode 2 and the aggregated electrode 3 were composed of first metal layers 2a, 3a made of copper and second metal layers 2a, 2b made of solder, respectively. An external connection terminal was simultaneously formed.

Electrical connection parts 20 were formed by resistance welding for electrical connections between the metal electrode 2, the external connection terminal and the aggregated electrode 3, respectively, to complete the optical circuit board. In this example 10, it was possible to arrange 80 number of the metal electrodes 2 in 8 number of the aggregated electrodes 3. In the same manner as in example 1, a light receiving device 13 was attached by bonding. There were no cracks and no separation was detected. According to the result of the reading test, it was confirmed that the reading activity was correctly carried out.

Example 11:

An optical circuit board was manufactured under the same conditions as Example 10, except for the condition for bonding the light receiving LSI chips 13 and the circuit board, the bonding conditions used were 5 kgf/cm², 150°C, press bonding for 5 minutes per lead of the light receiving LSI chips. No cracks and separations were detected in the binding region thus prepared. The reading test carried out later showed that the reading function was normal.

Example 12:

An optical circuit board shown in Fig. 12 was manufactured. This circuit board had a structure that was the same as in Fig. 10 of Example 10, but additionally had a protective layer 8 applied so as to cover a window portion 7 and an antistatic layer 6. The protective layer 8 was formed by applying and curing UV-curable urethane acrylic resin to a thickness of 10 µm after the aggregated electrode 3 and the antistatic layer 6 were formed.

Under the pressure of 10 kgf/cm² per terminal applied thereto, a lead of a light receiving device 13 was pressed to the metal electrode 2. By then taking in heated air by circulating heating (140ºC, 20 minutes), the light receiving device 13 was bonded to the circuit board. There were no cracks and no separation was detected. According to the result of the reading test, it was confirmed that the reading was carried out correctly.

Example 13:

An optical circuit board was manufactured with the same structure as shown in Fig. 12 of Example 12. On a first and second main surface of a Capton V film with a thickness of 25 µm, black chromium oxide with a thickness of 0.1 µm and a thin copper layer of about 1 µm thick were deposited sequentially by DC magnetron sputtering. The black chromium oxide layer consisted of a low-reflective layer 4.

On the thin copper layer formed on the first and second main surfaces, a predetermined pattern of the resist resin was applied. Then, a A perforation hole was made in the transparent substrate 1 with a perforator, a copper layer was formed on the inside of the penetrating hole by electroless plating to prepare an electrical connection part 20. By the above process, an electrical connection between a metal electrode 2 on the first main surface and an aggregated electrode 3 on the second main surface was completed. In addition, a copper layer of about 5 µm was formed on the above copper layer by electroplating. Then, after the resist resin was removed and unnecessary thin copper films were removed by etching, a solder layer comprising Sn-Pb alloy of about 2 µm thick was formed by substitution plating method. In addition, UV-curing urethane acrylic resin was applied and cured on the second main surface in a manner that it covered an antistatic layer 6 and a window part 7, thus forming a protective layer 8 having a thickness of 10 µm. In the metal electrode 2, the first metal layer 2a was composed of copper and the second metal layer 2b consisted of solder.

Thus, the complete circuit board and a light receiving device 13 were connected to a terminal by pressing and heating under the conditions of 5 kgf/cm², 150°C, held for 3 minutes. No cracks and separations were detected in the connecting part and it was confirmed that the reading device operated normally for reading.

Example 14:

An optical circuit board shown in Fig. 13 was prepared. This circuit board had a similar structure to that shown in Fig. 12 of Example 12, but differed from this circuit board of Fig. 12 in that a low-reflective layer was not provided in the first primary layer.

A PES film having a thickness of 30 µm with a thin copper film of 1 µm thick previously formed thereon on a first main surface by a sputtering method was used as the transparent substrate 1. A copper foil having a thickness of 18 µm with one side being treated to be black colored was coated on a second main surface of the transparent substrate 1 by a transparent epoxy base adhesive with the black colored side thereof facing the transparent substrate 1. The copper foil on the second main surface was covered with a mask and a predetermined pattern of a resist resin was applied to the thin copper foil on the first main surface. By electroplating, a solder layer of about 3 µm thick comprising Sn-Pb alloy was formed on the thin copper layer. Then, after removing the resist resin, the unnecessary thin copper foil was removed, thereby forming a metal electrode 2 and a darkening layer 5. It was arranged that an external connection terminal was also formed simultaneously on the first main surface. In the metal electrode 2, a thin copper film and a solder film correspond to the first and second metal layers 2a, 2b, respectively.

A protective mask on the second main surface was stripped off and the mask was applied to the first main surface. A predetermined pattern of resist ink was applied to the copper foil of the second main surface and unnecessary copper foil was removed by etching. By these processes, a plurality of aggregated electrodes of a predetermined shape and an antistatic layer 6 were provided so that a window part 7 was defined. Then, the mask on the first main surface was removed and the metal electrode 2 and the external connection terminal were welded to the aggregated electrode 3 by resistance welding. Finally, a protective layer 8 similar to that shown in FIG. game 5, provided on the second main surface so as to cover the window part 7 and the antistatic layer 6.

The connection of this circuit board and a light receiving LSI chip 13 was carried out by thermal heating by circulating air heating at a gas temperature of 120ºC. The bonding between an external driver board and the external terminal board was carried out under the conditions of 5 kgf/cm², 185ºC, held for 3 seconds. There was no separation in the bonded area and it was confirmed that the reader operated normally.

Example 15:

A circuit board shown in Fig. 14 was manufactured. This circuit board had a similar structure to that shown in Fig. 10, but differed in that the entire light-receiving LSI chips were covered with a transparent sealing resin.

On each of the first and second primary layers of a transparent substrate 1 which was a PES film of 50 µm thick, a black chromium oxide layer of 0.1 µm thick was formed as a low reflection layer 4 by a DC magnetron sputtering method, and then a thin copper film of 0.5 µm thick was formed. After resist resin was printed on each of the first and second main surfaces in the same pattern as in Example 7, a copper layer of about 5 µm thick was deposited on the thin copper film by electroplating, and then a thin layer of about 5 µm thick was formed thereon in the same manner as above. Then, the resist resin was removed, and unnecessary chromium oxide and the thin copper foil were removed by flash etching. By these processes, a metal electrode 2, an aggregated electrode 3, a darkening layer 5, and an antistatic layer 6 were formed. Here, the metal electrode 2 and the aggregated electrode 3 were made of a first metal metal layer of copper 2a and 3a and a second metal layer of tin 2b, 3b, respectively. At this time, the external connection terminal was also formed. The metal electrode 2, the external connection terminal and the aggregated electrode 3 were electrically connected in the same manner as in Example 5 and a protective layer 8 was provided in the same manner as in Example 9.

Light receiving LSI chips 13 with terminals made of gold were pressed onto the metal electrodes 2 with a pressure of 10 kgf/cm2 per pad and held at a temperature of 185°C for 30 seconds, and thus light receiving LSI chips 13 were bonded to the circuit board. Then, the thermosetting polyester base resin was applied to cover the entire light receiving LSI chips 13 and heated at 140°C for 20 minutes to harden the resin and form the hardened resin layer 10. In addition, an external driver circuit board was bonded to the external connection terminal in the same manner as above. As a result, no cracks and separations were detected in the bonding parts. With an optical reader attached to this circuit board, the light from the light source 12 transmitted through window part 7, irradiated on manuscript 14 placed on the second main surface, reflected from the manuscript 14 and transmitted through window part 7 was checked; the light was detected by light-receiving LSI chips 13 and read by the optical reader. As a result, it was confirmed that the reading function was normal.

Example 16:

A circuit board was prepared having a similar structure to that shown in Fig. 14 of Example 15.

On each of the first and second main surfaces of a transparent substrate 1, which is a PES film of 50 µm thick, a black nickel oxide layer of 0.1 µm thick was formed as a low reflection layer 4 by a DC magnetron sputtering method, and then a thin copper film of 0.5 µm thick was formed thereon. A resist resin was printed on the thin copper film on each of the first and second main surfaces with the predetermined patterns. Then, a perforation hole was formed with a perforator at the position where a metal electrode 2 and an aggregated electrode 3 were to be connected. By forming a copper layer on the inside of the penetration hole by electroless plating, the electrical connection between a metal electrode 2 and an aggregated electrode 3 was completed. Then, a copper layer of about 5 µm thick was formed thereon by electroplating, and then a nickel layer of about 2 µm thick was formed thereon, followed by a final gold layer of 0.2 µm thick in the same manner as above. Then, the resist resin was removed, and unnecessary nickel oxide and thin copper film were also removed. Through the above-mentioned process, the metal electrode 2, the aggregated electrode 3, a darkening layer 5 and an antistatic layer 6 were formed. Here, the metal electrode 2 and the aggregated electrode 3 were composed of first metal layers of copper 2a, 3a and second metal layers of nickel and gold 2b, 3b, respectively. The external connection terminal was also formed at the same time when the metal electrode 2 was formed. A protective layer 8 was formed in the same manner as in Example 9.

Light receiving LSI chips 13 with leads made of aluminum were pressed onto the metal electrodes 2 with the pressure of 10 kgf/cm² per pad and kept at a temperature of 185ºC for 30 seconds, thereby bonding the light receiving LSI chips 13 to the circuit board. Then, a thermosetting polyester base resin was applied to cover the entire light receiving LSI. chips 13 and to fill the gap between the circuit board and the light receiving LSI chips 13, then heated at 140ºC for 20 minutes to harden the resin and form the hardened resin layer 10. In addition, an external driver circuit board having a connection terminal made of a solder layer was bonded to the external connection terminal by pressing thereon with a pressure of 2 kgf/cm² and holding at a temperature of 180ºC for 30 seconds. As a result, no cracks and separations were detected in the connections. It was confirmed that the reading function was normal.

Example 17:

An optical circuit board was prepared as shown in Fig. 15. This circuit board had a structure similar to that shown in Fig. 11.

A copper foil having a thickness of 18 µm was immersed in an aqueous mixed solution of sodium hydroxide and potassium persulfate kept at 90°C for 20 minutes, and then a black coloring treatment was carried out on both sides of the copper foil. Molten PES having a thickness of 20 µm was extruded onto the copper foil through a T-die of an extruder, thereby forming a laminate consisting of the PES foil and the copper foil. Thus, the PES foil was made of a transparent substrate 1, and the copper foil was disposed on a second main surface of the transparent substrate 1.

On the PES film of the laminate, that is, on the first main surface of the transparent substrate 1, a nickel layer of 3 pn thickness (low-reflective layer 4) and a thin copper layer of 0.5 μm thickness were then formed by a DC magnetron sputtering process. This thin copper foil consisted of a first metal layer 2a of a metal electrode 2.

Then a mask was placed over the entire thin copper foil on the second main surface for protection and the resist resin was applied to the thin copper foil on the first main surface in a predetermined pattern. Then, a solder layer comprising a Sn-Pb alloy of about 5 µm in thickness was formed on the thin copper layer by electroplating in an alkanolsulfonate bath. This solder layer was a second metal layer 2b of the metal electrode 2. Then, the resist ink was removed, and thereafter, unnecessary nickel and the thin copper foil were removed by etching. By the above-mentioned operation, the metal electrode 2, a darkening layer 5 and an external connection terminal were provided on the first main surface.

Then, a mask for protection was placed on the first main surface, the mask on the second main surface was removed. Then, resist ink was applied to the copper foil on the second main surface in a predetermined pattern. After that, the copper foil was processed by etching and then the resist was removed to prepare an aggregated electrode 3 and an antistatic layer 6 having the darkening property. The aggregated electrode 3, the antistatic layer 6 each had a low reflection layer 4 consisting of a black colored layer on both sides thereof. Then, after the mask on the first main surface was removed, resistance welding was applied in the same manner as in Example 1 to electrically connect the metal electrode 2 and the external connection terminal, respectively, to the aggregated electrode 3. In addition, on the second main surface, a protective layer 8 was formed in the same manner to cover a window part 7 and the antistatic layer 6 in the same manner as in Example 3.

A light receiving device 13 was mounted on a circuit board as in Example 9 and the reading test was applied to a manuscript 14. As a result of the test, no cracks and separations were found in the connection part and it was confirmed that the reading could be adequately carried out according to the above procedure.

Example 18:

A circuit board was prepared as shown in Fig. 16. This circuit board is similar to that shown in Fig. 15, but differs in that a black insulating resin layer is provided on the surface of an aggregated electrode 3 and an antistatic layer 6 is provided as a low-reflective layer.

First, a copper foil having a thickness of 12 µm was prepared only on one side thereof, which was colored black. Then, a PES film having a thickness of 15 µm was formed on the black colored surface of the copper foil by a casting method. This PES film corresponded to a transparent substrate 1, and the copper foil was arranged on a second main surface of the transparent substrate 1. Thereafter, a nickel layer having a thickness of 0.05 µm (low-reflective layer 4) and a thin copper film having a thickness of 0.5 µm were successively formed on a first main surface of the transparent substrate 1 by a DC magnetron sputtering method.

Then, a mask for protection was coated over the entire copper foil on the second main surface. A resist film was stuck on the thin copper foil on the first main surface, a predetermined pattern was printed, and unnecessary resist was removed. Then, a solder layer comprising Sn-Pb alloy of about 3 µm in thickness was formed on the thin copper layer by electroplating in an alkanolsulfonate bath. Thereafter, the resist was removed, and thereafter unnecessary nickel and the thin copper foil were removed by etching. By the above-mentioned operation, the metal electrode 2, a darkening layer 5, and an external connection terminal were provided on the first main surface. A Window part 7 was defined by the metal electrode 2 and the darkening layer 5.

Then, a mask for protection was coated on the first main surface, the mask on the second main surface was removed. A black-colored thermosetting resin including carbon black was applied as a resist on the copper foil on the second main surface, which was printed on the copper foil with a predetermined pattern. After the resin was cured, the copper foil including the black-colored layer was etched. Through the above-mentioned process, an aggregated electrode 3 and an antistatic layer 6 having a darkening property defining the window part 7 were formed. The aggregated electrode 3 and the antistatic layer 6 each had a low-reflective layer 4 comprising a black-colored layer formed on the contact surface with the transparent substrate 1 and had a low-reflective layer comprising a black insulating resin layer 11 on the exposed side. After removing the mask on the first main surface, resistance welding was applied to electrically connect both the metal electrode 2 and the external connection terminal to the aggregated electrode 3. As a result of this, a number of 120 metal electrodes 2 were arranged into a number of 8 external connection leads. In addition, a UV-curable urethane acrylic resin was applied to the second main surface and formed into a protective layer 8 with a thickness of 20 µm.

Light receiving LSI chips 13 and an activating circuit board were connected to this circuit board in the same manner as in Example 1. In this case, no cracks and separation were detected at the connected part. By carrying out the reading test with respect to a manuscript 14, it was confirmed that the reading was carried out appropriately.

Example 19:

A printed circuit board shown in Fig. 17 was manufactured. This printed circuit board had a similar structure to that shown in Fig. 14, but differed in that a protective layer 8 was provided almost over the entire second major surface.

On each of the first and second main surfaces of a transparent substrate 1, namely a PES film having a thickness of 50 µm, a black chromium oxide layer having a thickness of 0.1 µm was formed as a low reflection layer 4 by a DC magnetron sputtering method, and then a thin copper film having a thickness of 0.5 µm D was formed thereon. A mask for protection was placed on the second main surface, and a resist resin was applied to the thin copper film on the first main surface in a predetermined pattern so that a metal electrode 2, a darkening layer 5 and an external connection terminal could be formed. Then, a solder layer having a thickness of 5 µm comprising a Sn-Pb alloy was formed on the first main surface by electroplating in the alkanolsulfonate bath. Thereafter, after the resist resin was removed, the unnecessary thin copper foil was also removed. Through the above-mentioned operation, the metal electrode 2, the darkening layer 5 and an external connection terminal were formed. By removing the mask from the second main surface, placing a mask for protection on the first main surface and performing the same treatment as performed in the first main surface, an aggregated electrode 3 and an antistatic layer 6 were formed. Here, the metal electrode 2 and the aggregated electrode 3 were composed of first metal layers of copper 2a, 3a and second metal layers of solder 2b, 3b, respectively.

Thereafter, a heating electrode head and a welding electrode head were contacted to the position where an electrical connection part 20 was to be formed, thereby forming an electrical Connection between metal electrode 2 and aggregated electrode 3 was made by resistance welding. Then, a UV-curable urethane acrylic resin was applied to the second main surface in a thickness of 15 µm in such a manner as to cover the entire surface of aggregated electrode 3, antistatic layer 6 and window part 7, thereby forming a protective layer 8.

On the first main surface, a thermosetting resin comprising silicone acrylate was applied around the window part 7 and the metal electrode 2. A plurality of light receiving devices 13 each comprising a semiconductor device having a connection terminal were applied to the predetermined metal electrodes 2, then held at a temperature of 150°C for 5 minutes under a pressure of 0.5 kgf/cm2 per device to connect the light receiving devices 13 and the metal electrodes 2 while curing the resin. Then, an external connection terminal and an external driver circuit board were pressed against each other, press-contacted to the corresponding terminals at a temperature of 190°C for 30 seconds for press bonding. As a result, no cracks and no separation were detected in the bonding areas. The light from a light source 12 was transmitted through the window part 7 and irradiated on a manuscript 14 which was moved facing the second main surface. Then, the light reflected from the manuscript was detected by a light receiving device 13 and read by an optical reading device. The reading function of the optical reading device was found to be normal.

Example 20:

A circuit board shown in Fig. 18 was manufactured. This circuit board is used for an optical imaging device and has a similar structure to that shown in the first embodiment, but differs in that a metal electrode 2 has a structure in which a first metal layer 2a and a second metal layer 2b are successively laminated on the side of a transparent substrate 1 and a protective layer 8 is not provided on the surface where an aggregated electrode 3 is formed and further a darkening layer 5 is also provided in the vicinity of the surface of the second metal layer 2b where the light emitting LSI chips 16 are mounted.

On each of the first and second main surfaces of a transparent substrate 1 made of a polyarylate film having a thickness of 50 µm, a thin copper film having a thickness of 0.5 µm was formed by a DC magnetron sputtering method. A resist resin was printed on the first and second main surfaces, respectively, in a predetermined pattern so that only a metal electrode 2 and an aggregated electrode 3 could be formed. Then, a copper layer having a thickness of 5 µm was formed by electroplating on both sides, and further, a solder layer comprising a Sn-Pb alloy of 5 µm thick was formed by electroplating in the alkanolsulfonate bath. Thereafter, after the resist resin was removed, unnecessary thin copper foil was also removed. By the above-mentioned operation, a metal electrode 2 and an aggregated electrode 3 were formed. These electrodes have a laminated structure consisting of first metal layers of copper 2a, 3a and second metal layers of solder 2b, 3b, respectively. Metal electrode 2 and the aggregated electrode 3 were pressed against each other by external force, thereby establishing their electrical connection.

Then, black paint enclosing resin was printed on the first main surface so as to define a window part 7, thereby forming a darkening layer 5 having good electrical insulation resistance. It was arranged so that the darkening layer 5 was also formed on the second metal layer 2b at the same time. Enclosing the soot particle The resin was applied to the second main surface in such a manner that the window portion was defined in the same manner as in Example 4, and was thermally cured to form an antistatic layer 6 having a darkening property. In addition, the protective layer 8 was provided on the second main surface so that the antistatic layer 6 and the window portion 7 are covered.

LED (light-emitting diode) arrays were used as the light-emitting LSI chips 16. Terminals of these LED arrays and the metal electrode 2 were pressed against each other with a pressing force of about 6 kgf/cm² and held at 140ºC for 4 minutes for bonding. There was no separation and no cracks in the bonding areas, and it was confirmed that this circuit board functioned smoothly as a head for an optical printer.

Example 21:

A circuit board shown in Fig. 19 was manufactured. This circuit board has a structure similar to that shown in Fig. 6 of Example 1, but with the difference that light-emitting LSI chips 16 for writing are mounted instead of light-receiving LSI chips and each metal electrode is composed of first and second metal layers 2a, 2b.

The circuit board was manufactured in the same steps as in Example 1. A thermosetting resin comprising silicone acrylate was applied to the first main surface around a window portion 7 and a metal electrode 2. A plurality of light-receiving LSI chips 16 each having a connection terminal and serving as an image-forming LED were placed on a predetermined metal electrode 2 and heated at a temperature of 150°C for 5 minutes under a pressure of 1 kgf/cm² to connect the light-emitting LSI chips 16 and the metal electrode 2 and to apply a silicone acrylate to cover the entire light-emitting chips 16 and to fill the gap between the circuit board 2 and the metal electrode 2. te and the light emitting LSI chips 16. No cracks and no separation were detected in the bonded part. Then, an external connection terminal on the first main surface and a connection terminal of an external activating circuit board were connected by a bonding process as described above. The normal operation of a photo printer was confirmed by using the light emitted from the light emitting LSI chips 16 onto a photosensitive surface 15.

Example 22:

A circuit board was manufactured as shown in Fig. 20 by modifying a circuit board shown in Fig. 19 so that an insulating shading layer 5 was formed by printing the resin with carbon black to define a window part 7 and together with it a glass fiber array 18 bonded to a second main surface through an adhesive layer 9 to complete an optical circuit board with a light guide. A UV-curable acrylate resin was used as the adhesive layer 9 and the glass fiber array 18 was arranged at the position corresponding to the window part 7. The shading layer 5 was also provided on the second metal layer 2b. A plurality of image-forming LEDs were used as a light-emitting device 16 which irradiated light onto a photosensitive surface 15 and tested. The test result proved that such a device normally operated as an optical image-forming device.

Example 23:

A circuit board shown in Fig. 21 was manufactured. This circuit board was of the same structure as that shown in Fig. 10, but differed in that light-emitting LSI chips were mounted instead of light-receiving LSI chips and a protective layer 8 was formed on the second main surface so as to cover an antistatic layer 6 and a window part 7.

On each of the first and second main surfaces of a transparent substrate 1 made of a polyarylate film having a thickness of 50 µm, a black nickel oxide layer (low-reflectance layer 4) having a thickness of 0.1 µm and a thin copper foil having a thickness of 0.5 µm were formed by a DC magnetron sputtering method. A resist resin was printed on the first and second main surfaces in a predetermined pattern to form a copper layer of about 5 µm thick on both surfaces by electroplating. Then, a solder layer comprising Sn-Pb alloy of about 5 µm thick was formed by electroplating in an alkanolsulfonate bath. After the resist resin was removed, unnecessary nickel oxide and thin copper film were also removed. By the above-mentioned method, a metal electrode 2, an aggregated electrode 3, a darkening layer 5, and an antistatic layer 6 and an external connection terminal were formed. The metal electrode 2 and the aggregated electrode 3 had a layered structure comprising first metal layers of copper 2a, 3a and second metal layers of solder 2b, 3b, respectively. The metal electrode 2 and the external connection terminal were electrically connected to the aggregated electrode 3 by resistance welding. In addition, a protective layer 8 having a thickness of 10 µm comprising a UV-curable urethane acrylic resin was provided on the second main surface in a manner that the protective layer covered the antistatic layer 6 and the window part 7.

LED arrays were used as the light emitting LSI chips 16. Terminals of these LED arrays and the metal electrodes 2 were pressed against each other in the same manner as in Example 21 by a pressing force of about 2 kgf/cm² and held at 160°C for 3 minutes for bonding. No separation or cracks were observed in the bonded parts. Then, the external connection terminal and a connection terminal of an external activating circuit board were connected to each other. Compared with the usual circuit board, the number of connections to the activating circuit board was reduced, and it was confirmed that the physical and electrical connection reliability was increased in accordance with the reduced number of connections. It was also confirmed that this circuit board operated normally when used with a head of an optical printer.

Example 24:

An optical circuit board of the second embodiment was manufactured as shown in Figs. 5A and 5B, respectively. On each of the first and second main surfaces of a transparent substrate 1 made of a polyarylate film having a thickness of 50 µm, a black nickel oxide layer (low reflection layer) having a thickness of 0.1 µm and a thin copper film having a thickness of 0.5 µm were formed by a DC magnetron sputtering method. Penetration holes were formed by drilling at the positions where a metal electrode 2 and an external connection terminal 30 were electrically connected to an aggregated electrode 3, respectively.

Subsequently, resist ink was applied to the area where a metal electrode 2, an aggregated electrode 3, an antistatic layer 6 and an external connection terminal 30 were not formed so that the above-mentioned items could be formed on both sides of the window part 7. In addition, a copper layer having a thickness of about 0.3 µm was formed on the inside of the surface of the penetration hole by electroless plating. Subsequently, a copper layer having a thickness of 5 µm was formed on the area excluding the resist forming area by electroless plating and further a solder layer comprising Sn-Pb alloy of about 5 µm thick, by electroplating in the alkanolsulfonate bath. After the resist resin was removed, unnecessary nickel oxide and thin copper film were also removed by etching. In this way, the metal electrode 2, the aggregated electrode 3, the antistatic layer 6 and the external connection terminal 30 were formed. On the first main surface, the window portion 7 was defined by the metal electrodes 2 arranged on both sides thereof. On the second main surface, the window portion 7 was defined by the antistatic layer 6. A protective layer 8 having a thickness of about 10 µm comprising a UV-curable urethane acrylate resin was provided so as to cover almost the entire area of the second main surface.

As the LED light-emitting chips 16, LSI chips using LEDs for image formation were used. Together with a thermosetting resin comprising silicone acrylate, a plurality of LSI light-emitting chips 16 were placed on the respective metal electrodes 2 and pressed under a pressure of about 2 kgf/cm² held at a temperature of 150°C for 5 minutes to bond the two. As a result, no separation and cracks were detected in the bonding part. In addition, an external connection terminal 30 and a connection terminal on an external activation circuit board were connected. After confirming that they were electrically connected to each other properly, it was confirmed that they worked very well as a recording head for an optical printer.

Example 25:

A printed circuit board was manufactured having a structure similar to that shown in Fig. 20 of Example 22. On each of the first and second main surfaces of a transparent substrate 1, namely, a PES film having a thickness of 50 µm, a black nickel oxide layer having a thickness of 0.1 µm was formed as a low-reflection layer 4 by a DC magnetron sputtering method and then nected, a thin copper film with a thickness of 0.5 umD is formed on it.

After a mask for protection was placed on a thin copper film on the second main surface and a predetermined pattern was printed from a resist resin on the first main surface, a copper layer of about 5 µm in thickness was formed on the first main surface by electroplating. Then, a solder layer of 5 µm in thickness comprising a Sn-Pb alloy was formed on the first main surface by electroplating in an alkanolsulfonate bath. Then, after the resist resin was removed, the unnecessary nickel oxide layer and thin copper film were also removed. By the above-mentioned process, a metal electrode 2, a darkening layer 5 and an external connection terminal were formed.

After removing the mask on the second main surface and placing a mask for protection on the first main surface, a predetermined pattern of a resist resin was printed on the second main surface and then a solder layer was formed by electroplating. Then, the resist resin was removed and unnecessary nickel oxide and thin copper film were removed one after another, thereby forming an aggregate electrode 3 and an antistatic layer 6. Here, the metal electrode 2 and the aggregate electrode 3 had the layered structure composed of a first metal layer of copper 2a, 3a and a second metal layer of solder 2b, 3b, respectively. At the same time, the light reflectance of the low-reflection layer 4 was 20%.

Thereafter, a metal electrode 2 or an external connection terminal was electrically connected to the aggregated electrode 3 by resistance welding. Thereafter, a UV-curable urethane acrylic resin was applied to the second main surface in a thickness of 15 µm in such a manner as to cover the antistatic layer 6 and a window part 7, thereby forming a protective layer 8.

LSI chips using LEDs with leads were used as light-emitting LSI chips 16 for image formation. Together with a thermosetting resin consisting of silicon acrylate, these light-emitting LSI chips 16 were pressed against the metal electrodes 2 at a temperature of 150°C for 5 minutes to connect the light-emitting LSI chips 16 to the metal electrodes 2 and at the same time, the resin was cured. After that, the external connection terminal and a terminal on an external activating circuit board were connected. No cracks and separation were detected in the connection area. By transmitting the light from the light-emitting LSI chips 16 through the window area 7 and irradiating it onto a photosensitive material 15 moved to face the second main surface, it was confirmed that the image-forming activity was normally carried out.

Example 26:

A circuit board shown in Fig. 22 was manufactured. This circuit board was constructed in the same manner as that shown in Fig. 12, but an insulating layer made of an electrically insulating material was provided on the second major surface instead of an antistatic layer.

On each of a first and second main surface of a transparent substrate 1, namely a PES film having a thickness of 50 µm, a black nickel oxide layer having a thickness of 0.1 µm was formed as a low reflection layer 4 by a DC magnetron sputtering method, and then a thin copper film having a thickness of 0.5 µmD was formed thereon. After a mask for protection was placed on a thin copper film on the second main surface and a predetermined pattern was printed by a resist resin on the first main surface, a copper Then, a solder layer of about 5 µm thick comprising a Sn-Pb alloy was formed on the first main surface by electroplating. Then, after the resist resin was removed, unnecessary nickel oxide layer and thin copper foil were also removed by etching. By the above process, a metal electrode 2, a darkening layer 5 and an external connection terminal were formed.

After removing the mask on the second main surface and placing a mask for protection on the first main surface, a predetermined pattern of resist resin was printed on the second main surface, and then a copper layer having a thickness of 5 µm and a solder layer having a thickness of 5 µm comprising a Sn-Pb alloy were formed by electroplating. After that, resist resin was removed, and then unnecessary nickel oxide and copper thin film were removed, thereby forming the aggregate electrode 3. Here, the metal electrode 2 and an aggregate electrode 3 were composed of the first metal layers of copper 2a, 3a and second metal layers of solder 2b, 3b, respectively.

Thereafter, the metal electrode 2 and the external connection terminal were electrically connected to the aggregated electrode 3 by resistance welding. A thermosetting resin containing a black pigment was applied to the second main surface in a manner that the resin defined a window region 7, and then the resin was cured, thereby forming a darkening layer 11 comprising a black insulating resin. Thereafter, a UV-curable urethane acrylic resin having a thickness of 15 µm was applied to the second main surface in a manner that it covered the darkening layer 11 and the window region 7, thereby forming a protective layer 8.

This circuit board and the light receiving LSI chips 13 with the terminals were connected in the same manner as in Example 1, and further, the external connection terminal and an activating circuit board were connected. There are no cracks and no separation was detected in the connection, however, when the reading test was carried out with respect to the manuscript 14, noise was generated when reading the manuscript 14, resulting in poor and improper reading. The reason for this was found to be that electric noise was generated due to static electricity caused by rubbing between the manuscript 14 and the circuit board. From this, it is understood that it is effective to provide the antistatic layer on the second main surface to prevent noise, particularly for articles having a structure in which a transparent resin protective layer is provided.

Example 27:

On each of the first and second main surfaces composed of a PES film having a thickness of 50 µm, a black nickel oxide layer (low reflection layer) having a thickness of 0.1 µm and a thin copper film having a thickness of 0.5 µmD were formed successively by a DC magnetron sputtering method. After a predetermined pattern of a resist resin was printed on both the first and second main surfaces, a copper layer having a thickness of about 5 µm was formed on the thin copper film. Thereafter, the above product was immersed in a solder bath at 240°C and an attempt was made to form a solder layer on the copper layer. However, the PES film constituting the transparent substrate contracted and practically no usable circuit board could be produced. Therefore, it is clear that a solder layer is to be applied to the metal electrode in order to facilitate the press bonding of the devices formed by such a to facilitate the plating process carried out at room temperature.

Example 28:

A printed circuit board shown in Fig. 23 was manufactured. This printed circuit board had a structure without an aggregated electrode. When this printed circuit board is connected to an external activating printed circuit board, each metal electrode of the printed circuit board and each connection terminal of the external activating printed circuit board are connected with one-to-one correspondence.

On a first main surface of a transparent substrate 1, namely, a PES film having a thickness of 50 µm, a black nickel oxide layer (low-reflective layer 4) having a thickness of 0.1 µm and a thin copper film having a thickness of 0.5 µmD were formed sequentially by a DC magnetron sputtering method. After a predetermined pattern of a resist resin was printed on the first main surface, a copper layer having a thickness of about 5 µm was formed on the first main surface by electroplating. Then, a solder layer having a thickness of 5 µm comprising a Sn-Pb alloy was formed on the first main surface. After the resist resin was removed, unnecessary nickel oxide and thin copper film were also removed by etching. Through the above-mentioned process, a metal electrode 2 having a laminated structure of a first metal layer 2a made of copper and a second metal layer 2b made of solder was formed. Here, 150 of the metal electrodes 2 each having a width of 0.9 mm were formed on one side of a window part 7.

Subsequently, a darkening layer 5 and an antistatic layer 6 were formed by printing a mixture of a thermosetting resin containing carbon black particles by screen printing on a first and second main surface and then heat-curing the resin. The darkening layer 5 was formed on the first main surface on one side of the window part 7. The antistatic layer 6 having a darkening property was formed on the second main surface so as to define the window part 7. In addition, a protective layer 8 was provided on the second main surface with a UV-curable urethane acrylic resin in a thickness of 15 µm in such a manner that the protective layer covered the antistatic layer 6 and the window part 7.

After bonding, the thus completed circuit board and a light receiving device 13 having a lead, each metal electrode 2 and each connection terminal of an activating circuit board were bonded as a group at a temperature of 195°C held for 30 seconds. However, the PES film constituting the transparent substrate 1 contracted during the above process. Consequently, some of the 150 electrodes could not be connected to the outer activating circuit board. Therefore, this circuit board is unable to normally serve as a reading sensor for an optical reading device.

Claims (38)

1. An optical circuit board for mounting a plurality of LSI chips (13) for emitting and/or receiving light, comprising: a transparent substrate (1), the transparent substrate including a slit-shaped window part (7) for transmitting light entering the substrate (1) and/or exiting from a said LSI chip (13) through the substrate (1); a plurality of chip connection electrodes (2) provided on a first main surface of the transparent substrate (1) to which the LSI chips (13) are attached in use, the chip connection electrodes (2) being elongated, each extending from the window part (7) in a direction perpendicular to the long side of the slit-shaped window part, the plurality of chip connection electrodes forming a plurality of rows parallel to each other on at least one of the long sides of the window part (7); a plurality of input/output connection electrodes (3), I/OCC electrodes, provided on a second main surface of the substrate (1), the I/OCC electrodes (3) being elongated, each extending in a direction parallel to the long side of the slit-shaped window part (7), the plurality of I/OCC electrodes forming a plurality of columns parallel to each other, the second main surface being opposite to the first main surface with respect to the transparent substrate (1), and the I/OCC electrodes (3) being provided on a region of the substrate (1) corresponding to the region of the first main surface carrying the chip connection electrodes (2), so that, viewed in plan view, the chip connection and the I/OCC electrodes define a grid pattern with intersections; electrical connection parts (26) penetrating through the transparent substrate in the areas of the intersection points, whereby each of the I/OCC electrodes (3) is electrically connected to a respective one or a plurality of chip connection electrodes (2) through one or a plurality of the electrical connection parts (26); and a plurality of external connection terminals (30) electrically connected to the respective ones of the plurality of I/OCC electrodes (3) and provided on the first main surface and/or the second main surface. 2. Optical circuit board according to claim 1, wherein the chip connection electrodes (2) are made of at least one metal, selected from gold, silver, copper, nickel, chromium, tungsten, tin, lead and solder or an alloy thereof. 3. Optical circuit board according to claim 1, wherein the chip connection electrodes (2) are constructed from a laminate having a first metal layer (2a) and a second metal layer (2b) formed on the first metal layer. 4. Optical circuit board according to claim 3, wherein each of the first and second metal layers (2a, 2b) is made of at least one metal selected from gold, silver, copper, nickel, chromium, tungsten, tin, lead and solder or an alloy thereof; and the second metal layer (2b) is formed in such a manner that one or more LSI chips can be attached thereto by press bonding or by hot bonding. 5. An optical circuit board according to claim 4, wherein the second metal layer (2b) is formed by gold plating or solder plating. 6. Optical circuit board according to claim 4, wherein the second metal layer (2b) is formed by printing a gold or silver or solder metal layer. 7. Optical circuit board according to claim 1, wherein the I/OCC electrode (3) is constructed from at least one metal selected from gold, silver, copper, nickel, chromium, tungsten, tin, lead and solder or an alloy thereof. 8. An optical circuit board according to any preceding claim, wherein the external connection terminals (30) are constructed of at least one metal selected from gold, silver, copper, nickel, chromium, tungsten, tin, lead and solder or an alloy thereof. 9. The optical circuit board according to claim 8, wherein the external connection terminals (30) are provided on the first main surface, and each external connection terminal (30) is electrically connected to the I/OCC electrode (3) and each I/OCC electrode (3) is connected to an electrical connection terminal (30) through a corresponding electrical connection part penetrating through the transparent substrate (1). 10. An optical circuit board according to any preceding claim, wherein a common electrode (36) and an external connection terminal (30a) electrically connected to the common electrode are both provided on the first main surface, and some of the chip connection electrodes (2a) are connected to the common electrode (36) instead of to the I/OCC electrodes (3). 11. An optical circuit board according to claim 1, wherein a common electrode (36) and a plurality of external connection terminals are provided on the first main surface and/or the second main surface, and some of the chip connection electrodes are connected to the common electrode, and each of the external connection terminals circuits are electrically connected to each or a respective one or a plurality of the I/OCC electrodes (3) and the common electrode. 12. An optical circuit board according to any preceding claim, wherein a darkening layer (5) for defining the window part (7) and preventing light from entering the transparent substrate (1) through an area other than the window part is provided on the first main surface and/or the second main surface adjacent to the window part (7). 13. An optical circuit board according to any one of claims 1-11, wherein a darkening layer (5) for defining the window part (7) and preventing light from entering the transparent substrate (1) through a surface other than the window part is provided on the first main surface on one side of the window part (7), and the chip connection electrodes (2) are provided on the opposite side of the window part (7) and adjacent thereto. 14. An optical circuit board according to any one of claims 1-11, wherein a darkening layer (5) for defining the window part (7) and preventing light from entering the transparent substrate through the area other than the window part is provided on the first main surface so as to be disposed on the chip connection electrodes (2) and on each space between the adjacent chip connection electrodes (2). 15. Optical circuit board according to claim 12, 13 or 14, wherein the darkening layer (5) is made of metal. 16. Optical circuit board according to claim 12, 13 or 14, wherein the darkening layer (5) is constructed from plastic containing soot particles or color pigment components. 17. An optical circuit board according to any preceding claim, wherein a conductive antistatic layer (6) is provided on the second major surface. 18. An optical circuit board according to claim 17, wherein the antistatic layer (6) is composed of a member having a darkening property and is provided so that the window part (7) is defined while preventing the light from entering the transparent substrate through a surface other than the window part. 19. Optical circuit board according to claim 18, wherein the antistatic layer (6) is made of metal. 20. Optical circuit board according to claim 18, wherein the antistatic layer (6) is made of resin with carbon black or metal particles dispersed therein. 21. An optical circuit board according to claim 18, 19 or 20, wherein the antistatic layer (6) is formed so as to enclose the periphery of the window part (7). 22. Optical circuit board according to one of claims 18-21, wherein the antistatic layer (5) extends in the longitudinal direction of the window part (7) on both sides thereof. 23. An optical circuit board according to any preceding claim, further comprising a light guide (18) provided on the second major surface for guiding light from the window part (7) and/or to the window part (7). 24. An optical circuit board according to any preceding claim, wherein a low reflection layer (4) is provided in the bonding interface between the chip connection electrodes (2) and the transparent substrate (1). 25. Optical circuit board according to any preceding claim, wherein a layer (4) with low reflection in the adhesive interface between the I/OCC electrodes (3) and the transparent substrate (1). 26. An optical circuit board according to any one of claims 12-16 or any one of claims 17-25 when dependent thereon, wherein a low reflection layer (4) is provided in the adhesion interface between the darkening layer (5) and the transparent substrate (1). 27. An optical circuit board according to claim 18 or any of claims 19-26 when dependent thereon, wherein a low reflection layer (4) is provided in the adhesion interface between the antistatic layer (6) and the transparent substrate (1). 28. An optical circuit board according to any one of claims 24, 25, 26 and 27, wherein the light reflectance of the low reflection layer (4) is 50% or less. 29. Optical circuit board according to one of claims 24, 25, 26, 27 and 28, wherein the layer (4) with low reflection is made of metal, a metal compound, a plastic or an organic compound. 30. An optical circuit board according to any preceding claim, wherein a transparent protective layer (8) is applied to the second main surface in such a way that the protective layer covers the window part (7). 31. Optical circuit board according to claim 18, wherein a transparent protective layer (8) is applied to the second main surface in such a way that the protective layer (8) covers the window part (7) and/or the antistatic layer (6). 32. An optical circuit board according to any preceding claim, wherein the transparent substrate (1) is constructed from a flexible, film-like material. 33. Optical circuit board according to claim 32, wherein the transparent substrate (1) is composed of at least one material selected from polyethylene terephthalate, polyethylene naphthalate, polyamide, polyether, polysulfone, polyethersulfone, polycarbonate, polyarylate, polyetherimide, polyetheretherketone, polyimide and polyparabanic acid or copolymer thereof. 34. Optical circuit board according to claim 32 or 33, wherein the thickness of the transparent substrate (1) is in the range 5 to 500 µm. 35. Optical circuit board according to claim 32 or 33, wherein the thickness of the transparent substrate (1) is in the range 10 to 200 µm. 36. Optical circuit board according to claim 32 or 33, wherein the thickness of the transparent substrate (1) is in the range 20 to 50 µm. 37. An optical reading device for optically reading a manuscript, including an optical circuit board according to any preceding claim, having one or more optical reading LSI chips with lead wires mounted thereon; the circuit board being arranged so that it traverses, with the longitudinal direction of the window part (7), the direction of intended relative movement of the manuscript with respect to the optical reading device. 38. An optical imaging device for optically forming an image on a photosensitive material, including an optical circuit board according to any one of claims 1-36, having one or more optical imaging LSI chips with the connection leads mounted thereon; the circuit board being arranged so that it traverses with the longitudinal direction of the window part (7) the intended direction in which the relative movement between the photosensitive material and the optical imaging device occurs.